承压后受力最均匀的形状是( )。
A．球形
B．圆筒形
C．正方形
D．椭圆形
参考答案：A
解析： 承压后受力最均匀的形状是球形。
It is a pity that the industrial cities _____ in the nineteenth century do not attract visitors.
A．to be built
B．having built
C．being built
D．built
