请教VERBAL REVIEW的两个问题

Verbal Review上一问题：8题，The rising of costs of data-processing operations at many finacial institutions has created a growing opportunity for independent companies to provide these services more efficiently and at lower cost.

A. The rising of costs

C. The rising cost

这道题我倒是选对了C.答案中也提到the rising of costs is wordy and awkward. 但是再看后面一道：17题，In the mid-1960's a newly installed radar warning system mistook the rising of the moon as a massive missile attack by the Soviets.

B. rising of the moon for a massive Soviet missile attack

E. rise of the moon as a massive Soviet missile attack

这道题答案就为B,而我错选咯E，搞不懂咯……如果这里两个都用的mistake for的话那用rise也应该是对的吧？

希望各路NR指点~

A. The rising of costs

C. The rising cost

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here the rising is a adj, modify cost, where in question 17, the rising is an n., different.

to state it more clearly, in question 8,the emphasis is on cost and in question 17, the emphasis is on rising.