OG详解-OG5 文法 Q30

Choice A is the best answer. The sentence emphasizes a similarity between P waves and S waves, noting that they both travel beneath Earth’s surface, thereby causing the ground to move.
Choice B is incorrect. The sentence emphasizes a difference between P waves and S waves, noting that P waves travel faster than S waves; it doesn’t emphasize a similarity between the two types of waves. Choice C is incorrect. The sentence emphasizes how P waves move; it doesn’t emphasize a similarity between P waves and S waves. Choice D is incorrect. While the sentence acknowledges that P waves and S waves start at the same point, it doesn’t emphasize a similarity; instead, the sentence emphasizes a difference between the two types of waves, noting that they behave very differently