There have been great changes in China s_____ it opened to the outside world thirty years ago.

问题描述:

There have been great changes in China s_____ it opened to the outside world thirty years ago.

There have been great changes in China SINCE(填空用大写标出以醒目) it opened to the outside world thirty years ago.
自从30年前改革开放以来,中国产生了巨大的变化.
since:自从什么以来,主句是现在完成时.
绝对准确,