The student wants to emphasize a difference between C-type and S-type asteroids. Which choice most effectively uses relevant information from the notes to accomplish this goal?
A
Planetary scientists classify asteroids into types, two of which are the C-type and the S-type.
B
Planetary scientists consider an asteroid’s composition (such as whether the asteroid is composed mainly of silicate minerals or carbon) when classifying it.
C
Roughly 17 percent of known asteroids are classified as S-type asteroids; another percentage is classified as C-type asteroids.
D
C-type asteroids are mainly composed of carbon, whereas S-type asteroids are primarily made up of silicate minerals.
Explanation
Correct answer: D.
Choice D is the best answer. The sentence emphasizes a difference between C-type and S-type asteroids, noting that C-type asteroids are mainly composed of carbon, while S-type asteroids are mainly composed of silicate minerals.
Why the other choices are wrong
Choice A
Choice A is incorrect. The sentence states that C-type and S-type are two types of asteroids, but it doesn’t emphasize a difference between them.
Choice B
Choice B is incorrect because it doesn’t directly mention C-type or S-type asteroids.
Choice C
Choice C is incorrect. While the sentence mentions that 17 percent of known asteroids are S-type asteroids, it doesn’t identify the percentage of asteroids that are C-type. Therefore, the sentence doesn’t emphasize a difference between the two types.