曲柄所受约束及荷载如图所示。铰支座A处反力方向一定沿直线（）。
A.AC
B.AE
C.AF
D.AG
参考答案：D
______on his past mistakes, Ted realized that he had stayed around the wrong people.
A．To reflect
B．Reflecting
C．reflected
D．being reflected
焊接低碳钢时，熔池的结晶可分为（）阶段、固液阶段和完全凝固阶段。
