Many studies have looked at \_\_\_\_ echinacea works to prevent or shorten the course of a cold, but none were conclusive.
Ahow well正確答案
Bwhat can
Cwhat good
Dof which
答案與詳解
為什麼答案是 A
「how well」引導名詞子句，作「looked at」的受詞，「well」為副詞修飾動詞「works」，語意為「效果有多好」，完全符合語法與句意。
載入中…
