问题补充：
Let’s discuss the problem after school.
A. talk to
B. talk about
C. know about
D. think about
答案：
A. talk to
(答案→)B. talk about
C. know about
D. think about
解析：根据题干，本句的意思是“让我们放学后讨论这个问题吧。”discuss是“讨论”。Talk to“与…交谈”，talk about“谈论”，know about“了解”，think about“考虑”。所以本题选B。
