[求助]og-57

lwei1016

57.   In astronomy the term “red shift” denotes the extent to which light from a distant galaxy has been shifted toward the red, or long-wave, end of the light spectrum by the rapid motion of the galaxy away from the Earth.

(A) to which light from a distant galaxy has been shifted

(B) to which light from a distant galaxy has shifted

(C) that light from a distant galaxy has been shifted

(D) of light from a distant galaxy shifting（A）

(E) of the shift of light from a distant galaxy

Choice A is best because it is idiomatic and because its passive verb construction, has been shifted, clearly indicates that the light has been acted upon by the rapid motion. In B, the active verb has shifted suggests that the light, not the motion, is the agency of action, but such a construction leaves the phrase by the rapid motion of the galaxy away from the Earth without any logical or grammatical function. In C, the construction the extent that light is ungrammatical; denotes the extent must be completed by to which. D incorrectly employs an active verb, shifting, and extent of light is imprecise and awkward. E is faulty because it contains no verb to express the action performed by the rapid motion.

不明白which从句中which指代什么？

rhod

指代extent.

to the extent  => the extent to which

vincent0330

the extent (to which light from a distant galaxy has been shifted toward the red)

= the extent (which light from a distant galaxy has been shifted toward the red to)

lwei1016

thanks!

hanson_luo

答案没有问题，我的问题是题目中的时态，这题为什么要用现在完成时呢？描述一个客观现象用一般现在时不是更好？

携隐

完成时表达的是a span of time的动作。光从遥远的星系过来的一路上都在shift，到了那个extent之前，已经shift了N久了，所以要用完成时吧。一般现在时表示的是那个时点的动作，你总不能说光只有在达到那个extent的瞬间才有shift的动作吧。