?請看下面這道題，是考查祈使句還是考查非謂語動詞：If they don’t understand it the first time, _________ over it again until they do. A. going??????????????? B. to go?????????????????????? C. gone???????????????????? D. go此題正確答案選D，其余幾項(xiàng)均有可能被誤選?？崭袂?/font> if 引導(dǎo)的是一個條件狀語從句，而在空格處無論是填A、B或C，它都是一個非謂語動詞短語，而不是一個句子，這樣一來，整個句子沒有主句，從而導(dǎo)致結(jié)構(gòu)不完整。若選D，則 go over it again until they do 則是一個句子(祈使句則是一個句子()，在此用作主語。又如： (1) If he likes to eat it, _________ him some more.A. give?????????????????????B. giving?????????????????? C. given?????????????????????D. to give

(2) If anyone calls, _________ them I’m not at home.

A. tell???????????????????????B. telling???????????????????C. told???????????????????????D. to tell(3) When your mother comes back, _________ her to come to school at once.A. ask??????????????????????B. asking??????????????????C. asked?????????????????????D. to ask(4) While the baby is sleeping, _________ your work as soon as possible. A. finish???????????????????B. finishing???????????????C. finished??????????????????D. to finish

答案均選A，空格前分別為 if, when, while 引導(dǎo)的狀語從句，空格處填動詞原形，構(gòu)成祈使句，用作句子主語。