中断的实现需要硬件和软件结合完成。构成中断系统的两个部分是中断装置和
A．中断屏蔽
B．中断定时装置
C．中断源
D．中断处理程序
参考答案：D
正四面体ABCD中，E、F分别是BC、AD的中点，那么EF与平面BCD所成的角的大小为______．
"The risk" mentioned in the text probably refers to ______.
A．a possibility that there will be more climate changes
B．a potential that sea level will possibly keep rising
C．temperature rises that are expected to affect all countries
D．a prediction warning human beings not to ruin the environment
