Question

【题目】People have changed their ways of life to protect the environment. (改为被动语态)

People's ways of life ________ changed to protect the environment.

Answer 1

【答案】have been

【解析】

句意：为了保护环境，人们改变了生活方式。

将原句改为被动语态，主语people's ways of life表复数概念，且时态为现在完成时，故此处应为现在完成时的被动语态have been done。故答案为have been。