Technologies such as microphones and inkjet printers are made using piezoelectric materials, which generate an internal

Choice B is the best answer. The convention being tested is end-of-sentence punctuation. This choice correctly uses a period to punctuate a declarative sentence that asks an indirect question ("The toxic nature of some of these materials recently led a team from the University of Sheffield to investigate how their use could be better regulated").

Choice A is incorrect because the structure requires a period and a declarative clause at the end of the sentence that states what the team investigated, not an interrogative clause that asks a direct question, such as "how could their use be better regulated?" Choice C is incorrect because it’s unconventional to use a question mark in this way to punctuate a declarative sentence. Choice D is incorrect because the structure requires a declarative clause at the end of the sentence that states what the team investigated, not an interrogative clause that asks a direct question, such as "how could their use be better regulated?"