题干
6. A notice was _____ in order to remind the students of the changed lecture time.
A：sent u
B：given u
C：set u
D：put u
答案(点此获取答案解析）
D
A：sent u
B：given u
C：set u
D：put u
满足
０，向量
的夹角为
，且
，则向量
与
的夹角为
