B
其實(shí)C 也是對(duì)的.
不定式作表語時(shí)一般不可以省去to,但：
當(dāng)主語部分有do,作“做”講,表語陳述做的事時(shí),不定式符號(hào)to 可以省去,也可以不省
如：
The first thing that you shoud do is (to) improve your English.
What you should do is (to) help them out
The first thing for you to do is (to) find out when the train leaves.
請(qǐng)?jiān)诳蛻舳擞疑辖窃u(píng)價(jià)點(diǎn)“滿意”即可哇塞，不是吧，又是你~ ^_^就是說C也對(duì)咯？哇塞， 不愿看到我呀？是的愿意啊，，，那這道題可不可以從must 后面加do的角度解釋？就是那個(gè)do喔喔~謝啦