It be essential that 后面一定用虛擬語氣，且句子謂語動(dòng)詞固定為(should) + 動(dòng)詞原型;

　　It was essential that the applications forms send back before the deadline.

　　53. We _D_ our breakfast when an old man came to the door.

　　A just have had B have just had C just had D had just had

　　when 還可以表示①剛..就… (有動(dòng)作先后關(guān)系)、②恰在此時(shí);

　　44. I had just started back for the house to change my clothes _D_ I heard voices.

　　A as B while C after D when

　　45. I felt somewhat disappointed and was about to leave, _C_ something occurred which attracted my attention.

　　A unless B until C when D while

　　64. It was essential that these application forms _D_ back as early as possible.

　　A must be sent B will be sent C are sent D be sent

　　非謂語動(dòng)詞與獨(dú)立主格：短語，句子(或者句子，短語)

　　1.當(dāng)短語部分有獨(dú)立主語，并且該主語不同于句子主語，這時(shí)短語結(jié)構(gòu)稱為獨(dú)立主格。(它最明顯的特點(diǎn)是短語部分有獨(dú)立的主語)。

　　獨(dú)立主格的結(jié)構(gòu)1：名詞(代詞)+ 分詞 [現(xiàn)在分詞、過去分詞]

　　現(xiàn)在分詞表示主動(dòng)的，正在進(jìn)行的行為;過去分詞表示被動(dòng)的，已經(jīng)完成的行為。 作題時(shí)要通過判斷動(dòng)作與名詞(代詞)之間的關(guān)系來確定是使用現(xiàn)在分詞還是過去分詞。當(dāng)動(dòng)作由名詞(代詞)發(fā)出時(shí)使用現(xiàn)在分詞，而名詞(代詞)是受動(dòng)者時(shí)則用過去分詞。

　　54. Silver is the best conductor of electricity, copper _B_ it closely.

　　A followed B following C to follow D being followed

　　49. All things _A_, the planned trip will have to be called off.

　　A considered B be considered C considering D having considered

　　call off 取消; cancel vt. 取消; 四級(jí)中的考點(diǎn)就是現(xiàn)在分詞和過去分詞的區(qū)別。

　　獨(dú)立主格的結(jié)構(gòu)2：with + 名詞(代詞)+ 分詞 [句子當(dāng)中作狀語]

　　36. After the Arab states won independence, great emphasis was laid on expanding education, with girls as well as boys _C_ to go to school.

　　A to be encouraged B been encouraged C being encouraged D be encouraged

　　as well as 和(相當(dāng)于and); be encouraged不會(huì)考。

　　動(dòng)詞不定式有預(yù)示將來行為的含義。to be encouraged 將要被鼓勵(lì);

　　been encouraged 已經(jīng)被鼓勵(lì)完了，與主句的謂語動(dòng)詞相對(duì);being encouraged 正在被鼓勵(lì)

　　2.短語部分沒有獨(dú)立主語，則短語結(jié)構(gòu)稱為非謂語動(dòng)詞。

　　非謂語動(dòng)詞的結(jié)構(gòu)：分詞(分詞短語)

　　句子的主語決定非謂語動(dòng)詞中的分詞是用主動(dòng)還是被動(dòng)形式。如果是句子的主語發(fā)出動(dòng)作，則使用現(xiàn)在分詞;如果動(dòng)作不是由句子的主語發(fā)出，則使用過去分詞。