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