Learning to write is learning to think. You don’t know things clearly you can write them

问题补充：

Learning to write is learning to think. You don’t know things clearly you can write them down.

A. unless

B. if

C. since

D. whether

答案：

(答案→)A. unless

B. if

C. since

D. whether

解析：unless 除非，如果不；if是否，如果；since由于，自从……以来；whether是否。句意：学习写作就是学习思考。如果你不能把它们写下来，你就不能了解事物。结合语境可知选A。