题干
— What time is it now?
— .
A：It is fine
B：It is May 8th
C：It is Monday
D：It's seven thirty
答案(点此获取答案解析）
D
— What time is it now?
— .
A：It is fine
B：It is May 8th
C：It is Monday
D：It's seven thirty
，且
与
垂直，
垂直，
与
的夹角的余弦值为（ ）