we are watching TV in the sitting room ()my mother is cooking dinner
问题描述：
we are watching TV in the sitting room ()my mother is cooking dinner
a.after b.before c.when d.while
答
d.while 表达“与此同时”之意那when也有同时的意思为什么不选c？对比的前后如果都是进行时，惯常用 while。单选题有时可接受的不止一个答案，目的是让你选最佳答案。