Some people think more of animals than wil

  his father had come, his face lit up.

A．Having heard

B．When he heard

C．Hearing

D．When hearing

（1）一列波长大于1m的横波沿着z轴正方向传播，处在x₁=1m和x₂=2m的两质点A、B的振动图象如图中虚线和实线所示．求该横波的波长和波速．

（2）如图所示，空气中有一横截面为半圆环的均匀透明柱体，其内圆半径为r，外圆半径为R，R=

2

r．现有一束单色光垂直于水平端面A射入透明柱体，只经过两次全反射就垂直于水平端面B射出．求透明柱体的折射率至少是多少？

帕金森病最多见的初发症状是（）。

A.肌强直

B.运动迟缓

C.姿势步态异常

D.眼睑阵挛

E.震颤

CD23的Fc受体是

A．FcαR
B．FcβR
C．FcγR
D．FctδR
E．FcεR

夏小正