题干
—Could you tell me______________ at the meeting? I didn't take part in it.
—Sorry, I don't know, either.
A：what he said
B：what did he say
C：what he says
D：what does he say
答案(点此获取答案解析）
A
的前n项和为
，且
=6，
=4， 则公差d等于（ ）