Question

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

1. A.
   unless
2. B.
   if
3. C.
   since
4. D.
   whether

Answer 1

A
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。
考点：连词辨析