A．Go to classroom early to show respect for the teacher.B．Go to classroom early so as n
A. Go to classroom early to show respect for the teacher.
B. Go to classroom early so as not to annoy the teacher.
C. Go to classroom early to find a seat she likes to take.
D. Go to classroom early to find a front seat.
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在双缝衍射实验中，若保持双缝SA和SB的中心之间的距离d不变，而把两条缝的宽度α略微加宽，则单缝衍射的中央主极大变窄，其中所包含的干涉条纹数目有可能变少。
A. 正确
B. 错误
Agriculture is the country's chief source of wealth, wheat______ by far the biggest cereal
A. is
B. been
C. be
D. being
The focus of this book is to develop ______.
A. writing skill
B. reading skill
C. speaking and listening skills
D. listening, speaking, reading and writing skills
两束频率相同、振动方向相同、传播方向相反的单色光波叠加后将会产生驻波现象。
A. 正确
B. 错误
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