在牙列拥挤病例中邻面去釉的禁忌症是（） A.轻中度牙弓间隙不足 B.牙齿较大或上下牙

（选修3-4选做题）

如图甲所示，O点为振源，OP=s，t=0时刻O点由平衡位置开始振动，产生向右沿直线传播的简谐横波。图乙为从t=0时刻开始描绘的质点P的振动图象。下列判断中正确的是       

A．该波的传播周期为（t₂- t₁）

B．0-t₂时间内，这列波的传播的距离为    

C．t=0时刻，振源O振动的方向沿y轴负方向    

D．t=t₂时刻，P点的振动方向滑y轴负方向

.

第二节：短文改错(共10小题，满分10分

I was walking home from school while suddenly                    86. ______________

it rained heavy. What should I do? I didn’t have an                  87. ______________

umbrella and a raincoat with me. I looked around and                88. ______________

see some students walking happily under their umbrellas.             89. ______________

They must listened to the weather forecast. I began to                90. ______________

run and caught in the rain. I kept running until                      91. ______________

I got to a bookstore which I could wait until the rain                 92. ______________

stopped and in the same time I could read my                      93. ______________

favorite books. After about half a hour,                           94. ______________

the rain stopped and I went home.                               95.______________

抗原不会使机体产生（）

A.补体

B.抗体

C.细胞因子

D.致敏淋巴细胞

E.淋巴因子

对投资者而言，风险最小的债券形式是( )。

A．金融债券

B．企业债券

C．国债

D．地方政府债券

下列说法中，与洋务运动后期在天津兴办开平煤矿的目的无关的是（）

A.为了学习西方先进科学技术

B.为了“求富”

C.为解决军事工业的燃料、运输问题

D.为了解决军事工业的资金紧张问题