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【单选题】
指出下列方程在空间中所表示的曲线A.
圆
B.
椭圆
C.
双曲线
D.
抛物线
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【简答题】人体测量的数据常以百分位数来表示人体尺寸等级，最常用的是以（）、（）、（）三种百分位数来表示。
【单选题】Two slants with the same height, mass and different obliquity are located on a smooth surface of a plane. The slant is also smooth. Two same objects slide down on the slant form the top and from the r...
A.
The momenta of two objects are equal at the bottom end of the slant.
B.
The kinetic energies of two objects are equal at the bottom end of the slant.
C.
For the system composed of the objects and the slant ( and the Earth) ,mechanical energy is not conservative.
D.
For the system composed of the objects and the slant, the horizontal momentum is conservative.
【简答题】It is a smooth thick substance that is put on sore skin or a wound to help it heal.
【简答题】Consider the ocean suce is a smooth plane between sea water (density 1000 kg/m3, sound speed 1500 m/s) and air (density 1.03 kg/m3, sound speed 330 m/s), assume underwater sound is normally incide...
【单选题】_______ is a smooth round opening for nerves and blood vessels.
A.
sinus
B.
foramen
C.
fossa
D.
fissure
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