如图，若AC是BD的垂直平分线，AB=5cm，BC=3cm，则四边形ABCD的周长是（ ）。
16cm
______ there is going to be a policy change _____ of those things is going to change.
A．Unless; few
B．Until; few
C．Unless; none
D．Until; none
钢丝绳固定端的压板不少于（）个。
A、3
B、1
C、2
D、4
