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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Courageous people think quickly and act without hesitation.
A．complaint
B．consideration
C．delay
D．anxiety
单项选择题
It is not easy to remain tranquil when events suddenly change you life.
A．calm
B．upset
C．steady
D．severe
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