Teachers need to strike a balance between instructing their students and letting them discover things for themselves.
A. bold
B. delicate
C. pleasant
D. regular
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He couldn’t why his son quit his well-paid job and started his own business.
A. figure out
B. work out
C. figure
D. look out
There are employment opportunities with private enterprises, state and local governments as well as organizations such as the Red Cross.
A. popular
B. nonprofit
C. profit
D. profitable
利用平面任意力系平衡方程，最多能求解（ ）个未知量。
A. 1
B. 2
C. 3
D. 4
下列说法错误的是（）
A. 力的投影方向与坐标轴正方向一致时，取正号
B. 力的投影方向与坐标轴正方向相反时，取负号
C. 力使物体绕某点顺时针方向转动时，力对该点的矩取正号
D. 力偶使物体顺时针方向转动时，力偶矩取负号
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