1

Problem

In 2014, Amelia Quon and her team at NASA set out to build a helicopter capable of flying on Mars. Because Mars’s atmosphere is only one percent as dense as Earth’s, the air of Mars would not provide enough resistance to the rotating blades of a standard helicopter for the aircraft to stay aloft. For five years, Quon’s team tested designs in a lab that mimicked Mars’s atmospheric conditions. The craft the team ultimately designed can fly on Mars because its blades are longer and rotate faster than those of a helicopter of the same size built for Earth.

According to the text, why would a helicopter built for Earth be unable to fly on Mars?

2

Clue

Look for signal words indicating a cause-and-effect relationship, such as because, since, due to, as a result, for, or consequently.

3

Sumup

Please summarize Problem, Hint, Clue

Choices

4

Choice-A

Choice A is correct. The text explicitly states, "Because Mars’s atmosphere is only one percent as dense as Earth’s," a standard helicopter won’t have enough air resistance (lift) to fly. This difference in atmospheric density is the core reason given for the failure of a standard helicopter.

Correct Because Mars and Earth have different atmospheric conditions

5

Choice-B

Choice B is incorrect. The text actually states the opposite: the successful Mars craft has blades that are longer than those built for Earth, meaning the Earth blades were too short to generate the necessary lift.

Wrong Because the blades of helicopters built for Earth are too large to work on Mars

6

Choice-C

Choice C is incorrect. While gravity is weaker on Mars, the passage never mentions gravity as the reason a standard helicopter fails. The text attributes the problem solely to the low atmospheric density.

Wrong Because the gravity of Mars is much weaker than the gravity of Earth

7

Choice-D

Choice D is incorrect. The text doesn’t discuss the overall size causing the issue; it specifically identifies the problem as the insufficient length and rotation speed of the blades for the given atmospheric density.

Wrong Because helicopters built for Earth are too small to handle the conditions on Mars

8

Answer

Option

A

9

Sumup

Please summarize choices

3

Hint

In relative pronouns, use “that” to define which thing you mean, and “which” to add extra info (often after a comma).

4

Sumup

Please summarize Problem, Hint, Clue

Choices

5

Choice-A

Choice A is correct. Used for defining (restrictive) clauses referring to things. “Flowers that bloom in spring” specifies which flowers we’re talking about.

Correct No change

6

Choice-B

Choice B is incorrect. Used for non-defining clauses and usually follows a comma. Here, we’re defining the flowers, so “which” is wrong.

Wrong which

7

Choice-C

Choice C is incorrect. “Who” is used for people, not things or animals. “Flowers” are non-human, so this doesn’t fit.

Wrong who

8

Choice-D

Choice D is incorrect. Shows possession (“the man whose car…”). Flowers don’t possess something in this clause.

Wrong whose

9

Step

Correct Answer - that

10

Answer

Option

A

11

Sumup

Please summarize choices