a pair of compasses it is easy to describe a circle.A. Having B. To have hadC. If you ha

问题补充：

a pair of compasses, it is easy to describe a circle.

A. Having

B. To have had

C. If you have

D. if having

答案：

A. Having

B. To have had

(答案→)C. If you have

D. if having

解析：句意“如果你有一只圆规，画一个圆就很容易了。”选A的话，前后逻辑主语不一致。故选C。