The student worked ________, but, to our disappointment, he still failed in the final examination．
A.as hard as possible
B.as hard as possibly
C.as hard as he can
D.so hard as he could
网友回答
A解析表达“尽可能……”时，可用“as…as possible”或“as…as sb．can/could”。从本句中动词所表示的时间来看，结构中应用过去时态，故排除C项。