已知实数a，b，则“ab≥2”是“a2+b2≥4””的[ ] A.充分不必要条件

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问题选择题

已知实数a，b，则“ab≥2”是“a²+b²≥4””的[ ]

A.充分不必要条件

B.必要不充分条件

C.充要条件

D.既不充分也不必要条件

答案

答案：A

选择题

善于奔跑的猎豹、狮等动物适宜生活在 [ ]

A．崇山峻岭

B．茂密的森林

C．开阔的草原

D．一望无际的沙漠中

单项选择题

Speaker A: I wonder what's happened to Jerry. He hasn't been around for at least two weeks.Speaker B: ______

A．Yes, two weeks halve passed before you know where you are.

B．Jerry is quite introvert. He doesn't like to let others know much about him.

C．Do you know the reason for his absence

D．He took a leave to see his mother in Europe.