题干
—I’m sorry to keep you waiting.
—Oh, not at all. I _____ here only a few minutes.
—Oh, not at all. I _____ here only a few minutes.
A：am
B：wa
C：have bee
D：will be
答案(点此获取答案解析）
C
的顶点
为
的双曲线，若
,且
，