情态动词表推测与义务 — 英语选择题
题目
Tom's classmate promised to return the borrowed book today, but it is already 10 p.m. and he hasn't shown up. Tom says, "He _______ have forgotten his promise—he is so careless that it is quite possible." Which choice best completes the sentence? A. can't B. must C. should D. needn't