2. 外语
  3. There is substantial evidence that certain forms of solar energy either now or within a few years will be economically competiti

There is substantial evidence that certain forms of solar energy either now or within a few years will be economically competiti

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问题 There is substantial evidence that certain forms of solar energy either now or within a few years will be economically competitive with conventional sources of heat and power.
选项 A、either now or within a few years will be economically competitive with conventional sources of heat and power
B、will either be economically competitive with conventional sources of heat and power within a few years or are so now
C、will be economically competitive with conventional sources of heat and power either now or within a few years
D、either are now economically competitive with conventional sources of heat and power or will be so within a few years
E、are either now or will be within a few years economically competitive with conventional sources of heat and power
答案D
解析 A、C中无论either…or连接的时间状语放在谓语之前(如A)或放在谓语之后(如C)，都易产生误解，使读者认为“现在或者在将来的几年内”这两个不同时段的时间状语共同修饰同一个表将来的谓语动词will be，这显然在修饰上是不可行的。另外，由于either…or结构要求并列成分的形式及功能的一致性(可查阅下一章“平行结构”)，把B代回原句，句子可简化为：will be or will are so now，显然后半部分的will are是不能接受的。E中的either之后是一时间状语now，or之后是整个谓语部分，两者的并列同样不能让人接受。而D中，either…or连接两个与不同时间段相对应的不同谓语部分的并列，这种表达不仅在语法上，而且在逻辑上都是正确的：即now和are对应，will be与within a few years，不会存在共用同一谓语的情况。其中so替代与前面相同的表语成分：economically competitive with conventional sources of heat and power。注意：本句的evidence是用同位语从句修饰的。
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