Last summer I took a course on _______ poisonous gases.

A．how to deal with

B．what to deal with

C．how to be dealt with

D．what to be dealt with

Rather than _______ on a crowded bus, he always prefers _______ a bicycle.   [ ]

A. ride； ride      

B. riding； ride   

C. ride； to ride    

D. to ride； riding