题干
I saw him in the library yesterday. He ________ a book at that moment.
A：reads
B：is reading
C：was reading
D：will read
答案(点此获取答案解析）
C
I saw him in the library yesterday. He ________ a book at that moment.
A：reads
B：is reading
C：was reading
D：will read
中，圆锥曲线 
的参数方程为 
（ 
为参数），定点 
， 
是圆锥曲线 