请教下大全语法第十章的三道题~

P307

28.Since savings banks have to use short-term deposits to finance long-term fixed-rate mortgage loans,they sometimes lose money when there is a rise in short-term rates and, on the other hand, they are unable to raise the rates on their mortgages.

A. when there is a rise in short-term rates and, on the other hand, they are unable to raise

B. when short-term rates rise and they are unable to raise

C. when a rise in short-term rates occurs and, correspondingly, there is no rise possible in

D. with a rise in short-term rates, and they are unable to raise

E. with short-term rates on the rise and no rise possible in

这题我的问题我原来选的E，因为我觉得B的指代有问题，when从句里面and连接的两个部分，后面的they are unable to raise岂不是指代前面的short-term rates?但是又和句尾on their mortgages产生矛盾？不解

P293

6.（偷懒下只打了答案）A newly developed jumpo rocket,which is expected to carry the United States into its next phase ofspace exploration, will be able to deliver a heavier load of instruments into orbit than the space shuttle can , and at a lower cost.

这句最后的at a lower cost.用and 连接，算什么意思，这不是明显不对称么，难道是省略了Be 东西？

P305

25. Even their most ardent champions concede that no less than a technical or scientific breakthrough is necessary before solar cells can meet the goal of providing one percent of the nation's energy needs.

A. that no less than a technical or scientific breakthrough is necessary

B. that nothing other than a technical or scientific breakthrough is needed

C. that a technical or scientific breakthrough is necessary

先打这3个，当时我选的是B，因为觉得C把原句的语气削弱了，但是后面解答又说它有累赘了。这个要怎么看，到底是累赘还是语气？

P307  they sometimes lose money when short-term rates rise
            and they
                are unable to raise the rates on their mortgages

这里对and的理解是个关键，and是连接两个动宾短语的连词，而动作的发出者都是they，即savings banks 而when short-term rates rise 只是时间状语修饰they sometimes lose money
            

25. A no less that与后面的necessary语意重复

    B nothing other than 与needed重复 而且needed没有necessary准确

    C没问题