UPPSC 2021 Prelims GS Paper-I · Question 105 of 150

Correct — B, Sumatra → Java → Bali → Lombok. These islands lie along the Sunda Arc on the southern edge of Indonesia. From west to east the order is Sumatra (the large western island), then Java (immediately south-east across the Sunda Strait), then the Lesser Sunda islands — Bali, and further east Lombok (separated from Bali by the Lombok Strait). So the west-to-east sequence is Sumatra, Java, Bali, Lombok.

• (a)Java, Sumatra, Lombok, Bali — Reverses two pairs — Sumatra lies west of Java (not east), and Bali lies west of Lombok (not east).
• (c)Sumatra, Java, Lombok, Bali — Sumatra and Java are placed right, but Bali is west of Lombok — Bali should come before Lombok, not after it.
• (d)Bali, Sumatra, Java, Lombok — Puts the small eastern island Bali first; the westernmost of the four is Sumatra.

Indonesia is the world's largest archipelago. Its main islands lie along the Sunda Arc, a volcanic chain formed where the Indo-Australian plate subducts beneath the Sunda plate. From west to east run Sumatra and Java, then the Lesser Sunda Islands (Bali, Lombok, Sumbawa, Flores, Timor). The Lombok Strait between Bali and Lombok marks the Wallace Line, a biogeographic boundary between Asian and Australasian species.

Order the islands by their strait boundaries: the Sunda Strait separates Sumatra and Java, and the Lombok Strait separates Bali and Lombok. Knowing that Bali sits immediately west of Lombok (the Wallace Line) resolves the trap between options (b) and (c).

• West-to-east along the Sunda Arc: Sumatra → Java → Bali → Lombok
• Sunda Strait separates Sumatra and Java; Lombok Strait separates Bali and Lombok
• The Lombok Strait (Bali–Lombok) marks the Wallace Line — Asian vs Australasian biota
• All four lie on the volcanic Sunda Arc (Indo-Australian plate subduction)

• Reversing Bali and Lombok — Bali is west of Lombok
• Placing Java west of Sumatra — Sumatra is the westernmost of the two

Asked as 'arrange the islands/features from west-to-east (or another direction)' — fix the strait boundaries (Sunda Strait, Lombok Strait/Wallace Line) to order them.

No directly related past PYQ was found.

• practice — not a real PYQ

  The Wallace Line, separating Asian and Australasian fauna, runs through which strait?

  • (a)Sunda Strait
  • (b)Lombok Strait
  • (c)Malacca Strait
  • (d)Palk Strait

  Answer(b) the Lombok Strait, between Bali and Lombok.

• practice — not a real PYQ

  The Sunda Strait separates which two Indonesian islands?

  • (a)Java and Bali
  • (b)Sumatra and Java
  • (c)Bali and Lombok
  • (d)Sumatra and Borneo

  Answer(b) Sumatra and Java.