单项选择题

When I try to understand _____that prevents so many Americans from being as happy as one might expect, it seems to me that there are two causes.

A．why it does
B．what it does
C．what it is
D．why it is
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单项选择题
There are few electronic applications _____to raise fears regarding future employment opportunities than robots.
A．likely
B．more likely
C．most likely
D．much likely
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