Our research has focused on a drug which is so _____ as to be able to change brain chemistry. A. powerful B. influential C. monstrous D. vigorous
答案:A. powerful 解析: powerful (=having or producing great power) 强有力的。在这里四个形容词中, 只有powerful (有效力的) 可与表示药物的名词搭配。influential 有影响的, 有势力的, monstrous 异常大的, vigorous 精力旺盛的, 强健有力的。