OG详解-OG5 文法 Q16

Choice B is the best answer. The convention being tested is punctuation use between a subject and a verb. When, as in this case, a subject (“the strings inside the instrument”) is immediately followed by a main verb (“are plucked”), no punctuation is needed.
Choice A is incorrect because no punctuation is needed between the subject and the verb. Choice C is incorrect because no punctuation is needed between the subject and the verb. Choice D is incorrect because no punctuation is needed between the subject and the verb.