单选题
1.【阅读选择】Good news for chocoholics:the treat preferred by millions all over the world is good for you,according to American researchers at the University of California.Chocolate contains substances called flavonoids（类黄酮） that can help maintain a healthy heart and good circulation.The researchers have discovered that cocoa acts like aspirin and that eating a bar of chocolate has also been shown to release endorphins in the body:these chemicals help to reduce pain and stress and make you feel happy.
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.
正确答案：B
答案解析：因果关系词信号词。凡是注释中文的地方可能是答案区域。