MPSC 2025 Prelims Paper-I · Question 30 of 100

Correct — option (3), 'a – ii, b – iv, c – i, d – iii,' pairs each ocean with the deepest trench actually found in it. The Pacific Ocean (a) pairs with the Mariana Trench (ii): the Mariana Trench, in the western Pacific near Guam, contains the Challenger Deep, the deepest known point in any ocean on Earth, at roughly 10,900-11,000 metres. The Atlantic Ocean (b) pairs with the Puerto Rico Trench (iv): this trench, north of the island of Puerto Rico, holds the Atlantic's deepest point (the Brownson/Milwaukee Deep) at around 8,300-8,400 metres. The Indian Ocean (c) pairs with the Java Trench (i), also called the Sunda Trench: running along the southern coast of Java and Sumatra where the Indo-Australian plate subducts beneath the Sunda plate, it is the Indian Ocean's deepest feature, reaching roughly 7,200-7,450 metres. The Arctic Ocean (d) pairs with the Eurasian Trench (iii): the Arctic's deepest water lies in the Eurasian Basin, whose deepest known point (the Molloy Deep, in the Fram Strait between Greenland and Svalbard) reaches roughly 5,500 metres, making it by far the shallowest of these four 'deepest points' — consistent with the Arctic being the shallowest of the world's oceans overall. Each pairing follows the same underlying logic: every major ocean has one characteristic deep trench or basin that geography questions use as its identifying feature, and this item simply asks a candidate to hold all four in memory at once.

• (1)a – iv, b – iii, c – ii, d – i — Every single pairing here is wrong. It assigns the Puerto Rico Trench to the Pacific (it is Atlantic), the Eurasian Trench to the Atlantic (it is Arctic), the Mariana Trench to the Indian Ocean (it is Pacific), and the Java Trench to the Arctic (it is Indian Ocean). This option is best read as a near-total scramble of the correct set rather than a plausible partial match.
• (2)a – i, b – ii, c – iii, d – iv — This option pairs the oceans with the trenches in the exact order they are listed (a-i, b-ii, c-iii, d-iv) rather than by their actual geography, and every pairing is wrong as a result: the Java Trench is Indian Ocean, not Pacific; the Mariana Trench is Pacific, not Atlantic; the Eurasian Trench is Arctic, not Indian Ocean; and the Puerto Rico Trench is Atlantic, not Arctic. It is the kind of straight-sequence option a rushed candidate can be drawn to precisely because it looks orderly, not because it is correct.
• (4)a – ii, b – iii, c – iv, d – i — This option gets the Pacific-Mariana pairing right but gets the remaining three wrong: it assigns the Eurasian Trench to the Atlantic (it belongs to the Arctic), the Puerto Rico Trench to the Indian Ocean (it belongs to the Atlantic), and the Java Trench to the Arctic (it belongs to the Indian Ocean). Getting one of four pairings right is exactly why this option is a believable distractor — a candidate confident about Mariana-Pacific but unsure of the other three can land here without noticing the remaining mismatches.

Each of the world's major oceans has a defining deepest trench or basin: the Pacific's Mariana Trench (Challenger Deep, ~10,900-11,000 m, the deepest point on Earth), the Atlantic's Puerto Rico Trench (~8,300-8,400 m), the Indian Ocean's Java/Sunda Trench (~7,200-7,450 m), and the Arctic's Eurasian Basin, whose deepest point is the Molloy Deep (~5,500 m). These four form a fixed, frequently-tested fact set in physical geography, and the depths themselves also rank the oceans from deepest (Pacific) to shallowest (Arctic).

MPSC and UPSC both favour trench-matching questions because oceanography is compact enough to test as pure recall while still discriminating between candidates who have only memorised 'Mariana Trench is deepest' and those who know the complete four-ocean set. The examiner's trap is almost always structural rather than factual: scrambling known pairings (as in options 1 and 4 here) or presenting them in a deceptively tidy sequential order (option 2) rather than inventing false trench names, since a genuinely fabricated name would be too easy to spot.

• Pacific Ocean — Mariana Trench, containing the Challenger Deep at roughly 10,900-11,000 m, the deepest point in any ocean.
• Atlantic Ocean — Puerto Rico Trench, roughly 8,300-8,400 m deep, north of the island of Puerto Rico.
• Indian Ocean — Java Trench (Sunda Trench), roughly 7,200-7,450 m deep, along the southern coast of Java and Sumatra.
• Arctic Ocean — Eurasian Basin, whose deepest known point (Molloy Deep, in the Fram Strait) reaches roughly 5,500 m, making it the shallowest of the four 'deepest points.'
• The four trenches/basins rank in the same order as their parent oceans' overall depth: Pacific > Atlantic > Indian > Arctic.

• Assuming the trench names are listed in an order that matches the oceans, rather than checking each pairing independently
• Confusing the Java/Sunda Trench (Indian Ocean) with Pacific trenches near similar latitudes, since both lie in seismically active subduction zones
• Treating the Arctic's shallower 'deepest point' as an error rather than recognising it correctly reflects the Arctic being the shallowest ocean overall

MPSC's Paper-I oceanography questions return to the deepest-trench-per-ocean fact set across editions, almost always as a four-way match-the-columns item like this one rather than single-fact recall, because holding all four pairings simultaneously is what actually separates prepared candidates from those who know only the headline Mariana Trench fact. The safest preparation is to fix the four ocean-trench-depth triples together as one table rather than learning any single pairing in isolation.

No directly related past PYQ was found.

• practice — not a real PYQ

  The Challenger Deep, the deepest known point in any of the world's oceans, lies within which trench ?

  • (a)Java Trench
  • (b)Puerto Rico Trench
  • (c)Mariana Trench
  • (d)Tonga Trench

  Answer(c) Mariana Trench — the Challenger Deep, in the western Pacific near Guam, reaches roughly 10,900-11,000 m, the deepest point recorded in any ocean.

• practice — not a real PYQ

  Which ocean's deepest point is found in the Eurasian Basin, at the comparatively shallow depth of around 5,500 m ?

  • (a)Southern Ocean
  • (b)Arctic Ocean
  • (c)Indian Ocean
  • (d)Atlantic Ocean

  Answer(b) Arctic Ocean — its deepest known point, the Molloy Deep in the Fram Strait, lies within the Eurasian Basin, consistent with the Arctic being the shallowest of the world's major oceans overall.