单项选择题

Why is chocolate good for heart and circulation

A．It reduces pain and stress.
B．It contains substances called flavonoids.
C．It releases endorphins in human body.
D．It acts like aspirin to protect heart.

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热门试题

单项选择题

Scientists at Camegie Mellon University tried to find out ______.

A．why office doors were often left open
B．when it was a good time to turn off the computer
C．what questions office workers were bothered with
D．which behaviors could tell whether a person was busy

单项选择题

During the experiment, the subjects were asked______.

A．to control the sensors and the camera
B．to rate the degrees to which they could be interrupted
C．to compare their behaviors with others'
D．to analyze all the indicators of interruption