It’s necessary to be prepared for a job interview. the answer ready will be of great help

问题补充：

It’s necessary to be prepared for a job interview. the answer ready will be of great help.

A. To have had

B. Having had

C. Have

D. Having

答案：

A. To have had

B. Having had

C. Have

(答案→)D. Having

解析：考查非谓语动词。句中Having the answer ready为动名词短语作主语，句意：准备工作面试时有必要的，准备好回答是很有帮助的。