Swimming is good for our health 游泳有益于健康 用It be+adj+to do sth替换: It is good for our health to swim. ( It ) can be difficult ( to swim ).游泳很难. 这样改下来,结构对了,但是意思完全不对啊!
It is good for our health to swim.用It be+adj+to do sth替换啊It is good for our health to swim. 就是It be+adj+to do sth这个结构啊。只不过根据句意中间插入了for our health 。 希望能帮到你,祝你进步。但是要根据句中空白部分你是说 “____can be diffcult___...