单项选择题

Lighting levels are carefully controlled to fall within an acceptable level for optimal reading convenience.

A．ideal
B．required
C．optional
D．standard
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单项选择题
Factors leading to the crisis included poor regulation, mismanagement and deception in the industry, and competition from other types of financial firms.
A．cheating
B．pollution
C．depression
D．abuse
单项选择题
Courageous people think quickly and act without hesitation.
A．complaint
B．consideration
C．delay
D．anxiety
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