What he should do = What he ought to do
如:What he should do is to close the door = What he ought to do is to close the door.
再问： Ҫ������ʵ�
再答： ���: ����ô, ����ⷢ��������.......
再问： The poor boy doesn't know what he should do The poor boy doesn't know___ ___ ____
再答： ���: The poor boy doesn't know ( what to do )
