题干
Have you ever played jokes _____ others _____April Fool's Day?
A：in, in
B：on, on
C：at, at
D：to, to
答案(点此获取答案解析）
B
Have you ever played jokes _____ others _____April Fool's Day?
A：in, in
B：on, on
C：at, at
D：to, to
绕原点逆时针旋转
后可得到双曲线
．据此类推可求得双曲线
的焦距为