时间知觉是人脑对运动物体的延续性和顺序性的知觉。
参考答案：对
I ____________ a cold, and my sister has a fever.[ ]
A. have
B. has
C. had
下列制冷工质是混合工质的是（）
A、R22
B、R407c
C、R134a
D、R123
