some kinds of fish release some black liquid to protect themselves from being killed.(保持句意不变)
问题描述：
some kinds of fish release some black liquid to protect themselves from being killed.(保持句意不变)
some kinds of fish protect themselves from being killed _____ ______ some black liquid.
答
by releasing
通过释放请问，为什么是by ？有什么语法包含在里面吗？通过什么，用by doing原句意思是：一些鱼释放黑色液体来保护他们自已不被杀。同义可表达：一些鱼通过释放黑色液体保护他们自已不被杀。