要保持头脑敏锐，我们就必须经常阅读并积极思考。

A.Weshouldoftennotdosomereadingandthinkactivelyinordertokeepourmindssharp.

B.Weshouldoftendosomereadingandthinkactivelyinordertokeepourmindssharp.

C.Weshouldoftendofewreadingandthinkactivelyinordertokeepyourheadsharply.

D.Weshouldoftendomanyreadingandthinknegativelyinordertokeepyourmindssharp.

正确答案：A