Alternative Fuels for Emission Reduction Questions and Answers

Answer: A

Natural gas is mostly methane and is stored at around two hundred bar. The last option explains exactly that, which makes it a correct and more detailed version. Liquefied petroleum gas is a different mixture. Most errors here come from carrying across a result from a neighbouring case where it does not hold. A symptom that appears under one condition and not another is what narrows the diagnosis quickly. Working one numerical case through both cases side by side fixes the distinction better than any rule of thumb.

Answer: B

Liquefied petroleum gas liquefies at a few bar, unlike methane. The last option explains exactly that property, which makes it a correct and more detailed version of the same answer. Naming what changes and what stays the same is the reliable route through questions of this shape. The order in which the effects act is what decides the outcome, so it is worth establishing first. The shared properties explain why these belong to one family, and the differences explain why more than one exists.

Answer: C

Propane and butane liquefy at a few bar while methane needs hundreds. The last option explains exactly that difference, which makes it a correct and more instructive version of the same answer. Working the distinction through on a single concrete case fixes it more firmly than any rule of thumb. Checking which component actually carries the load settles most questions of this kind at once. Reading the definition literally, rather than recalling a formula, is the reliable route through questions of this shape.

Answer: D

Methane has the best hydrogen to carbon ratio of any hydrocarbon. The last option explains exactly that advantage, which makes it a correct and more instructive version. It still produces carbon dioxide. A symptom that appears under one condition and not another is what narrows the diagnosis quickly. The shared behaviour explains why these belong together and the differences explain why both exist. Reading the definition literally, rather than recalling a formula, is the reliable route through questions of this shape.

Answer: A

Methane is many times more potent than carbon dioxide as a greenhouse gas. The last option explains exactly why slip matters, which makes it a correct and more instructive version of the same answer. The order in which the effects act is what decides the outcome, so it is worth establishing first. Naming the cost of a choice alongside its benefit is what turns a fact into a design decision. Reading the definition literally, rather than recalling a summary, avoids the usual confusion.

Answer: B

Methane is unusually stable and needs a dedicated catalyst formulation. The last option explains exactly that difficulty, which makes it a correct and more instructive version of the same answer. Checking which component actually carries the load settles most questions of this kind at once. Reading the definition literally, rather than recalling a summary, avoids the usual confusion. A single measurement chosen to respond to the one asymmetry beats several that respond to shared behaviour.

Answer: C

The methane molecule is unusually stable and needs a high catalyst temperature. The last option explains exactly that, which makes it a correct and more instructive version of the same answer. Tracing the requirement back to the physical constraint that produces it makes the answer follow. Most errors here come from carrying across a result from a neighbouring case where it does not hold. Working one numerical case through both cases side by side fixes the distinction better than any rule of thumb.

Answer: D

Methane resists knock far better than petrol. The last option explains exactly the benefit that follows, which makes it a correct and more instructive version of the same answer. The shared behaviour explains why these belong together and the differences explain why both exist. Naming what changes and what stays the same is the reliable route through questions of this shape. A limit that survives making every external component ideal is an intrinsic one, and worth knowing for that reason.

Answer: A

A dedicated engine can raise its compression ratio and recover efficiency. The last option explains exactly that, which makes it a correct and more instructive version. Bi-fuel conversions cannot. Naming the cost of a choice alongside its benefit is what turns a fact into a design decision. Working the distinction through on a single concrete case fixes it more firmly than any rule of thumb. Reading the definition literally, rather than recalling a summary, avoids the usual confusion.

Answer: B

A bi-fuel engine must keep a compression ratio the petrol can tolerate. The last option explains exactly that limitation, which makes it a correct and more instructive version of the same answer. Reading the definition literally, rather than recalling a summary, avoids the usual confusion. A symptom that appears under one condition and not another is what narrows the diagnosis quickly. Checking the units of each quantity catches a wrong formula before the arithmetic begins.