SSC CGL 2025 Tier-I · 15 September 2025, Shift 3 · General Intelligence and Reasoning · Question 1 of 100

We transcribed this text from the pictures on a candidate's response sheet for this shift; the answer is the key SSC colour-marked on that sheet. Solution last reviewed 11 September 2026.

Where this paper and its answers come from

SSC does not publish CGL question papers or a public answer key. From 2025 the candidate response sheet prints every question and option as a picture, so the text here is transcribed from those pictures for this shift and checked against them independently; where the layout carries meaning, the picture is shown as well. Each answer is the key SSC colour-marked on that sheet. SSC released a tentative key for challenge and later its final one, both only to candidates behind a login, and the sheet does not say which of the two it carries. The solutions are written by UnlockIAS.

In the following question, select the related word from the given alternatives. Mercury : Thermometer :: Fuel : ?

(a)Fire
(b)Power
(c)Engine
(d)Oil

Answer

Why

Correct — C.
Rule: substance : the device that runs on it.

A thermometer works by mercury: the metal expands as it warms and climbs the narrow glass tube.
An engine runs on fuel: burning it releases the energy the engine turns into motion.

Fuel : Engine repeats Mercury : Thermometer → option (c).

Why the others are wrong

(a)
Fire — Fire is what burning fuel produces, a result. In the first pair Thermometer is a device that holds mercury, so the blank needs a device too.
(b)
Power — Power is what an engine delivers, an output. The first pair names the device itself, not what the device produces.
(d)
Oil — Oil is itself a substance, and some oils are fuels, so it belongs on Fuel's side of the pair. The blank needs the device, as Thermometer is.

Concept

Name the relation in the given pair as a sentence: mercury is what a thermometer works by. Then drop the third term into the same sentence: fuel is what an ___ runs on. Engine fits.

The wrong options each change the relation. Fire and Power are what fuel and engines produce, and Oil sits on the substance side with Fuel.

Engine, Power and Fire all belong in a sentence about fuel. The first pair decides which link is wanted, and it pairs a substance with a device.

Key facts

Mercury is the only metallic element that is liquid at standard temperature and pressure.
A liquid-in-glass thermometer reads temperature from how far its liquid expands up a narrow tube.
A petrol or diesel engine turns the energy released by burning fuel into mechanical work.

Study next

Instrument : quantity measured analogies, such as Thermometer : TemperatureDevice : what it produces analogies, such as Generator : ElectricityWorker : tool analogies

Common traps

Choosing Power because engines and power go together in everyday speech
Choosing Oil, a kind of fuel, which pairs the wrong halves of the analogy

14 Sep 2025, 09:00, Reasoning Q.1 puts the thermometer in a different relation: Clock : Time :: Thermometer : ?, keyed Temperature, a device and what it measures.

Here the thermometer sits on the device side and mercury on the substance side, so read each pair's relation afresh.

Related PYQs

No directly related past PYQ was found.

Topic: Semantic Analogy — all 42 SSC CGL questions on it, every solved shift.