Johny, you ________ play with the knife. You ________ hurt yourself. (NMET 1996)

[　　]

Sir, you ________ be sitting here in this waiting room. It's for women and children only. (NMET 1996)

[　　]

The number of people invited fifty ________, but a number of them ________ absent for different reasons. (NMET 1996)

[　　]

Sir, you ________ be sitting here in this waiting room. It's for women and children only. (NMET 1996)

1. A.
   oughtn't to
2. B.
   can't
3. C.
   won't
4. D.
   needn't