关于带to 的情态动词

maizai

7 W+ D3 Z; \) J7 Q* Q8 j. o% B' a带to 的情态动词有四个：ought to, have to, used to, be to, 如加上have got to ,(=must), be able to，为六个。它们的疑问，否定形式应予以注意： # g3 U1 U) N: I* J5 a　 Do they have to pay their bill before the end of the month? ) |3 j0 z6 }2 ~4 R　 She didn't use to play tennis before she was fourteen. : r7 J% F6 G7 q, C/ b　 You ought not to have told her all about it. 　 Ought he to see a heart specialist at once.? 8 \' K0 F. \$ w- B' @ 　 ought to 本身作为情态动词使用。其他的词作为实义动词使用，变疑问，否定时，须有do 等助动词协助。 6 O1 `2 J9 H( L9 F$ [: n 典型例题 " p5 Q# j+ y0 B+ G: N. a3 V: f　Tom ought not to ___ me your secret, but he meant no harm.　 / d$ W* j0 U6 C1 s# X# k　A.have told　B.tell　C.be telling　D. having told 　答案A。由于后句为过去时，告诉秘密的动作又发生在其前因，此地应用过去完成时，但它在情态动词 ought to 后，所以用have。