The word they in the first sentences of the third paragraph refers to________. A. chips B. tissues C. voltages D. researchers

Đáp án D.

Key words: they. first sentences, third paragraph, refers

Clue: “Researchers hope that eventually they will be able to develop more advanced chips whereby they can choose a particular voltage to activate particular tissues …"

Vậy ta chọn đáp án D. researchers.