itis形容词that句型虚拟should可以省
itis加形容词that从句都用虚拟语
itbe形容词that虚拟
it is adj that虚拟
it is high time that虚拟语气 should可以省
itisnecessarythat虚拟语气
itistimethat的虚拟语气
it is 形容
itissuggestedthat虚拟
itisessentialthat虚拟
