—What do you think we can do for our aged parents?

—You __ ___   do anything except to be with them and be yourself.[ ]

A. don’t have to  

B. oughtn’t to    

C. mustn’t

D. can’t

脑膜炎奈瑟菌的抗原组成不包括

A．荚膜多糖群特异性抗原
B．外膜蛋白型特异性抗原
C．鞭毛蛋白抗原
D．脂多糖抗原
E．核蛋白抗原