等腰三角形的两个内角之比是1∶2，那么这个等腰三角形的顶角度数为（ ）。
90°或36°
Mr Smith was almost broken down by________unfortunate events that happened to him.[ ]
A．a range of
B．a variety of
C．a series of
D．a list of
做出动力臂和阻力作用线．
