问题
选择题
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
题目分析：句意：学习写作就是学习思考。你不能清楚地知道事情除非你可以把他们写下来。Unless除非；if如果； since从；whether是否。所以选A。