新概念英语第三册 17课语法请先耐心看完这一段：he Verrazano Bridge,which was design

新概念英语第三册 17课语法
请先耐心看完这一段：
he Verrazano Bridge,which was designed by Othmar Ammann,joins Brooklyn to Staten Island.It has a span of 4,260 feet.Two great towers support four huge cables.The towers are built on immense underwater platforms make of steel and concrete.The platforms extend to a depth of over 100 feet under the sea.Above the surface of the water,the towers rise to a height of nearly 700 feet.They support the cables from which the bridge has been suspended.Each of the four cables contains 26,108 lengths of wire.It has been estimated that if the bridge were packed with cars,it would still only be carrying a third of its total capacity.
提问1：They support the cables from which the bridge has been suspended.是怎么回事?the bridge has been suspended from the cables?我没出要用from的原因
提问2：It has been estimated that if the bridge were packed with cars,it would still only be carrying a third of its total capacity.为什么是be carrying?我知道这句是虚拟,但是前面已经虚拟了,这和后面那句没什么关系吧?