问题
选择题
When I got there, he _____ them to dance. [ ]
A. is teaching
B. teaches
C. was teaching
D. taught
答案
答案：C
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When I got there, he _____ them to dance. [ ]
A. is teaching
B. teaches
C. was teaching
D. taught
答案：C
与圆x2+y2=12交于A、B两点，过A、B分别作l的垂线与x轴交于C、D两点，则|CD|=（）。