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。