The text is too difficult. All of us ________ understand it.

1. A.
   needn't
2. B.
   mustn't
3. C.
   may
4. D.
   can't

The text is ______ difficult ______ I can't understand it.

[    ]

　　A. too, to   B. too, that   C. enough, to   D. so, that

The text is too difficult. All of us ________ understand it.

[　　]

The text is too difficult. All of us ________ understand it.

[　　]