单项选择题

(That) the sun (but) not the earth (is) the center of our planetary system (was) a difficult concept to grasp in the Middle Ages.

A．That
B．but
C．is
D．was
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单项选择题
The growth (of) part-time and flexible working patterns (allow) more women (to) (take) advantage of employment opportunities.
A．of
B．allow
C．to
D．take
单项选择题
I regret (to spend) (so) much money (on) a car (that) I hardly drive in everyday life.
A．to spend
B．so
C．on
D．that
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