频率为100Hz,传播速度为400m/s的平面简谐波,波线上两点振动的相位差为1/4π,则此两点间的距离是()m。
A.2
B.0.5
C.1
D.1.5
参考答案:B
He sat there_________, with his head on his hand. [ ]
A. and think
B. thinking
C. thought
D. being thought
目前国家禁止()和()进入拍卖市场。