The nations that _______actively ________(involve) in earthquake prediction programs include Japan,Russia,and the United States. are involved

　　There __________(estimate) to be more than 20,000 overseas domestic servants working in Brtain in 1995. were estimated

　　3)動詞的語氣：

　　A.掌握非真實條件句中，謂語動詞在主句和條件句中的虛擬語氣形式。

　　If you had come earlier,you ______ (not miss) the first act of the play.

　　would not have missed

　　If it hadn't been for your help,we _____(be) in real trouble.

　　would have been

　　B.在表示建議、命令、要求以及表示“重要性”和“緊迫性”等含義的主語從句、賓語從句、表語從句和同位語從句中，謂語動詞常用虛擬語氣，由“動詞原形”或“should + 動詞原形”構成。 should 常常省略

　　I would recommend that you _______(think) about doing something similar for yourself. (should) think

　　It was imperative that students ______(finish) their papers before July 1st.

　　(should) finish

　　C.動詞wish 、would rather (sooner)、if only、as if 后的虛擬語氣。

　　I would rather he _____(buy) the house next year.

　　bought ( 表示從句中動作尚未發生)

　　She treats me as if I ______ (be) a stranger. were