题干
— Were you at home _________?
— No, I was at school.
A：two days before
B：two days ago
C：before two days
D：ago two days
答案(点此获取答案解析）
B
— Were you at home _________?
— No, I was at school.
A：two days before
B：two days ago
C：before two days
D：ago two days
＝
，则cos 
＝( )．