Global warming caused by human activities?a major concern for people all over the world.
问题描述：
Global warming caused by human activities?a major concern for people all over the world.
为什么是has become不应该是have become吗?定语从句的先行词是Global warming 还是 human activities
答
Global warming是主语,后面caused by human activities是定语
由人类活动造成的全球变暖