1.By 1999,the population had reached 6 billion,and by 2003 it had _______ to 6.3 billion.
A.rose B.raised C.risen D.rise
2.How I wish I _______ hear beethovem himself ____the music.
A.can,to play B.can,plays
C.could,play D.could,playing
3.A:Did you notice Susan _______ your room last night?
B:No, it's impossible.I heard she ______ on a trip yesterday morning.
A.enter into,went B.entering,go
C.enter,going D.enter,went
请简述答题方法，谢谢。

1.By 1999,the population had reached 6 billion,and by 2003 it had _______ to 6.3 billion.
A.rose B.raised C.risen D.rise
选C。过去完成时had risen。
rise表“上升”为不及物动词，rise---rose(过去式)---risen（过去分词）.
raise为及物动词，“把…举起，抬起”，raise---raised(过去式）---raised(过去分词）。

2.How I wish I _______ hear beethovem himself ____the music.
A.can,to play B.can,plays
C.could,play D.could,playing
选C。
当所表达的是一种愿望,希望得到的东西与现实不一样,wish后面的句子要用虚拟语气，表现在或将来时，动词用过去式(be 动词用were)；表过去时，动词用过去完成时。（建议阅读语法中的虚拟语气）
如：I wish I were a bird. I wish I had a big house.
I wish I had been there with you last week.
第二个空，hear sb. do表示听到某人做（全过程）
hear sb. doing 表示听到某人正在做某事。
这里指希望能听到贝多芬本人拉这首曲子，当然不表示瞬间正在了。

3.A:Did you notice Susan _______ your room last night?
B:No, it's impossible.I heard she ______ on a trip yesterday morning.
A.enter into,went B.entering,go
C.enter,going D.enter,went
选D。
第一个空表示“注意到Susan进你房间去了”，而不是“注意到她正在进你房间”；所以用notice sb. do sth而不用doing。另外，enter into表示“讨论、处理；参加”，不符合题意。
第二个空，hear这里为听说，后面用she，所以是hear后加宾语从句；时间状语是yesterday morning，且主句heard为过去式，从句中用谓语动词当然应用过去式went。