—How can I learn more about computer science?

—You can learn by _____ questions. [ ]

A. asked

B. asking

C. be asked

D. ask

小剂量药物的粉碎或实验室规模制备散剂，一般常用粉碎器械是

A．流能磨
B．球磨机
C．研钵
D．万能粉碎机
E．冲击式粉碎机