what we should do和what can we 可以换着用吗?

what we should do和what can we 可以换着用吗? what should we do? we do should what we should do what we can protect the enviroment we should do what we can protect the environment We should do what we can ( ) those in trouble . What can we do WHAT CAN WE DO? What should we do before meals?What should we do what should we do today What should we do?那个“should”可以换成“shall”吗? what+we+should+do+和what+should+we+do+的区别