题目内容

肠道螺旋瓣实际上是向肠腔内突起所形成（）

A. 黏膜层
B. 黏膜层和黏膜下层
C. 浆膜层
D. 基底膜

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下列鱼中那种鱼有的有发电器官（）

A. 鲨
B. 鳐
C. 鲤
D. 鮟鱇

I drop a 60-g golf ball from 2.0 m high. It rebounds to 1.5 m. How much energy is lost（）

A. 0.29 J
B. 0.50 J
C. 0.88 J
D. 1.0 J
E. 2.0 J
F. 1.5 J

A 550 N physics student stands on a bathroom scale in an 850 kg （including the student） elevator that is supported by a cable. As the elevator statts moving, the scale reads 450 N. The acceleration of

A. 17.82m/s^2, upward
B. 17.82m/s^2, downward
C. 1.78m/s^2, upward
D. 1.78m/s^2, downward

A professional skier reaches a speed of 56 m/s on a 30° ski slope. Ignoring friction, what was the minimum distance along the slope the skier would have had to travel, starting from rest（）

A. 110 m
B. 160 m
C. 320 m
D. 640 m