B.what to do
what to do是特殊疑問(wèn)詞加不定式組成的短語(yǔ),作句子的賓語(yǔ).又如：
I don't know when to come.
I don't understand why to take part in the party.
Can you tell me how to finish the homework?
A項(xiàng)應(yīng)改成what I should do,也就是改成陳述語(yǔ)氣.
C項(xiàng)應(yīng)改成what I do,道理同上.
關(guān)于陳述語(yǔ)氣和疑問(wèn)語(yǔ)氣：
He likes English.這是一個(gè)陳述句,是陳述語(yǔ)氣.
把它變成一般疑問(wèn)句就是：Does he like English?
這個(gè)句子是陳述語(yǔ)氣.它借了一個(gè)助動(dòng)詞did提到主語(yǔ)前面.
又如：
He is a teacher.(陳述語(yǔ)氣）----Is he a teacher?（疑問(wèn)語(yǔ)氣,系動(dòng)詞is提到主語(yǔ)前面了.）