30. --- Mrs. Smith, please teach me how to draw on the computer today. 

--- Oh, no._______. You have to get familiar with the keyboard first.

A．It is never too old to learn

B．Think twice before you do

C．Learn to walk before you run

D．One today is worth two tomorrows

男性，60岁。有萎缩性胃炎。组织学检查有不典型增生，最好采取的措施是（）

A.消除病因

B.用药物治疗

C.手术治疗

D.对症治疗及定期随访观察

E.应用抑酸药