Question

read the passage. there are several questions about this passage.
this excerpt is from a book that explains the science of everyday objects like tall buildings, bicycles, and automobiles
from atoms under the floorboards
1
one billion cars on the planet. count them! stack them on top of one another and youd get a pile 170,000 times higher than mount everest—tall enough to reach to the moon four times over. park them bumper to bumper and theyd stretch across the united states more than 1,200 times. a billion (a thousand million) is the kind of number most of us find hard to picture. to put it in some kind of perspective, the worlds population is a smidgen over 7 billion; between us, we guzzle 2 billion cups of coffee a day. there are roughly 6 billion mobile phones in circulation—and anywhere between 1 and 2 billion sheep. if you can get past a mental image of a sheep tucked behind the wheel of a jaguar, bleating into the mobile phone thats clamped, cloven hoof - style, to its jaw, can you possibly imagine a billion cars?
2
the interesting thing for me isnt that there are so many cars in the world, but why. what is it about cars thats made them, in the space of just over a century, one of the most successful inventions of all time? not surprisingly, the answer is all to do with science.
whats so good about cars?
3
cars are chemistry labs on wheels. and though that might not sound so interesting, it accounts absolutely for their ubiquity. take away the leather seats, the gleaming chrome, the go - faster stripes and all the rest, and youre left with a handful of tin cans called cylinders, where petrol explodes into power. cars are built around engines, and engines (or internal combustion engines, to give them their full name) burn petrol with oxygen in the air to release the energy locked inside it. we think of burning as a way of making fire, but its essentially a chemical reaction between oxygen and fuel that just
part a
this sentence is from the passage
\cars are built around engines, and engines (or internal combustion engines, to give them their full name) burn petrol with oxygen in the air to release the energy locked inside it.\ (paragraph 3)
what does the word it refer to in this sentence?
○ 1. the engine
○ 2. the petrol
○ 3. the oxygen
○ 4. the air
part b
which detail from paragraph 3 best supports the correct answer from part a?
○ 1. \explodes into power\
○ 2. \burning as a way of making fire\
○ 3. \a chemical reaction\
○ 4. \just happens to produce heat\

Explanation:

Part A

To determine what "it" refers to, we analyze the sentence: "engines... burn petrol with oxygen in the air to release the energy locked inside it". The energy is locked inside the petrol (since petrol is the fuel being burned to release energy). So "it" refers to petrol.

We need a detail from paragraph 3 that supports the answer from Part A (petrol is what "it" refers to). The sentence "engines... burn petrol with oxygen in the air to release the energy locked inside it" and the explanation that burning is a chemical reaction between oxygen and fuel (petrol is the fuel) relates to option 3: "a chemical reaction" as burning petrol (fuel) with oxygen is a chemical reaction that releases energy from petrol.

Answer:

1. the petrol

Part B