请教2提885提

bettyofarim

4.    Developing nations in various parts of the world have amassed $700 billion in debts; at stake, should a significant number of these debts be repudiated, is the solvency of some of the world’s largest multinational banks.
(A) should a significant number of these debts be repudiated, is
(B) should a significant number of these debts be repudiated, are
(C) should they repudiate a significant number of these debts, are
(D) if there is a repudiation of a significant number of these debts, would be
(E) if a significant number of these debts will be repudiated, is
答案 A，为什么呢？怎么觉得should 和is 在同一句中是两个谓语呢？

6.    There is ample evidence, derived from the lore of traditional folk medicine, that naturally occurring antibiotics are usually able to be modified to make them a more effective drug.
(A) are usually able to be modified to make them a more effective drug.
(B) are usually able to be modified to make them more effective drugs
(C) are usually able to be modified, which makes them more effective drugs
(D) can usually be modified to make them a more effective drug
(E) can usually be modified to make them more effective drugs
答案是E，请问这里的are usually able to 与can usually 从意思上有什么不同吗？

g4yLee

4这是个倒装句,should引导的是条件从句(插入),相当于if...正常句式应该是:should a significant number of these debts be repudiated, the solvency of some of the world’s largest multinational banks is at stake.

6be able to 强调主观能动,表示有能力去做什么, can表示可以,能,会.i am able to make money,i can make money.前者更强调有挣钱的能力,后者语气就弱很多.细细体会一下,我也说不好.这个句子里,antibiotics 肯定不会有能力去做或者被做...的

bettyofarim

明白了,谢谢!

lizaz

be able to是不能加被动语态的，好象have to be done 也是错误的。