要看具體語境.
It is/was ＋adj./n.＋that主語從句多數(shù)情況下用虛擬語氣,表達(dá)一種要求,命令或者責(zé)備,建議,或主觀看法.that 從句用“should+do,英國英語可以省略should”e.g.It is important that he (should) go to school.
但是如果只是表示陳述一個事實(shí)而不是強(qiáng)烈的感情,完全可以用一般的陳述語氣.
It is strange that he had made a mistake.（陳述一個事實(shí)：他犯了錯誤讓人有點(diǎn)奇怪.）
It is strange that he (should) have made a mistake.（虛擬語氣,說話者是在責(zé)備他本不應(yīng)該犯錯.）
e.g.It is a shame that the rain spoiled our picnic.\It is a pity (that) he lost so much money.\He was a very brave man and it is surprising that he lived so long.\It is strange that nobody knows where he lives .
特別注意that從句謂語動詞用“(should) + 動詞原形”的情況：
1."It is important (necessary,strange,impossible,natural) that ."
e.g.It's necessary that we should have a walk now.\It's natural that she should do so.\ It's important that we should take good care of the patient.
2."It is a pity (a shame,no wonder,better) that ."
e.g.It was a great pity that you (should) have made so many mistakes in your math exercise.\It will be better that she stay with her grandmother.
3."It is suggested (requested,proposed,ordered) that ."
e.g.It was suggested that the sports meet be put off until next Saturday.\It is desired that we (should) get everything ready by tonight.\It was ordered that the medicine be sent there by plane.