It has been proved __ eating vegetables in childhood helps to protect you against serious
　　illnesses in later life.
　　A. if
　　B. because
　　C. when
　　D. that

　　The telephone _______, but by the time I got indoors, it stopped.
　　A. had rung
　　B. was ringing
　　C. rings
　　D. has rung

— Are you ready for Spain?
　　— Yes. I want the girls to experience that _______ they are young.
　　A. while
　　B. until
　　C. if
　　D. before

　　My sister, an inexperienced rider, was found sitting on the bicycle ______ to balance it.
　　A. having tried
　　B. trying
　　C. to try
　　D. tried

　　As his best friend, I can make accurate guesses about _______ he will do or think.
　　A. what
　　B. which
　　C. whom
　　D. that

　　Something as simple as ____ some cold water may clear your mind and relieve pressure.
　　A. to drink
　　B. drinking
　　C to be drinking
　　D. drunk

So much of interest _______ that most visitors simply run out of time before seeing it all.
　　A. offers Beijing
　　B. Beijing offers
　　C. does Beijing offer
　　D. Beijing does offer

We went through a period ____ communications were very difficult in the rural areas.
　　A. which
　　B. whose
　　C. in which
　　D. with which

It is usually warm in my hometown in March, but it ________ be rather cold sometimes.
　　A. must
　　B. can
　　C. should
　　D. would

The teacher____have thought Johnson was worth it or she wouldn't have wasted time on him, I suppose.
　　A. should
　　B. can
　　C. would
　　D. must

答案：D　　解析：“must have+动词+ed形式”表示“一定做了某事”。根据所提供的情景or she wouldn’t have wasted time on him可判断出老师一定认为Johnson值得教，要不她不会在他身上浪费那么多时间。“should have+动词+ed形式，，表示“本来应该做某事，而没有做”，常用于表示责备。"can have+动词+ed形式”表示“可能做了某事”。would用于表示虚拟、假设、条件等，有“要、将要、会、就会”等意思。

This washing machine is environmentally friendly because it uses ___ water and electricity than ___ models.
　　A. less; older
　　B. less;elder
　　C. fewer; older
　　D. fewer; elder
　　答案：A
　　解析：little用于修饰不可数名词，few修饰复数可数名词。water是不可数名词，要用little修饰。再根据than可确定用比较级。表示比老型号的洗衣机用的水和电少。older表示年龄大或时间长，意为“较老的”。elder用于表示人的出生顺序，意为“年长的”。

She went to the bookstore and bought _____.
　　A. dozen books
　　B. dozens books
　　C. dozen of books
　　D. dozens of books
　　答案：D
　　解析：dozen意为“一打，十二个”，与数词连用时要用单数形式。与of连用时要用复数形式。dozens of意为“若干，许许多多”。

— When do we need to pay the balance?
　　— ____ September 30.
　　A. In
　　B. By
　　C. During
　　D. Within
　　答案：B
　　解析：by意为“到…为止”，指到9月30日为止。in表示一段时间，后接表示年、月或一段时间的名词，不表示日，所以不能作为答案。during意为“在…期间”，后接表示一段时间的名词。within与in意思基本相同，着重表示在某段时间内。