一定频率的超声波通过声速低的材料时,其波长将比通过声速高的材料时()。
A、一样
B、增长
C、减短
D、成倍增长
参考答案:C
考考你的课文理解能力,请根据课本P77 Lesson 62 Confidence的课文内容选择正确答案完成下列句子。
1.Peter stood ___ when his teacher talked to him.
A.at his desk
B.inthe front of the teacher's desk
C.in front of the teacher's desk
D.at the back of the classroom
2.What are around many of the words Peter wrote?
A.A mark crossing.
B.A square.
C.Some black circles.
D.Some red circles.
3.The word "____"was spelled "bot"by Peter.
A.bought
B.but
C.brought
D.boilt
下列哪项表皮为黏膜组织
A. * * B.阴阜C.大阴唇D.处女膜E.小阴唇