the place at which the bridge is supposed to be built should be where the cross river

问题描述:

the place at which the bridge is supposed to be built should be where the cross river
traffic is the heaviest.这句子咋分析?the place at (which the bridge should be )这是定从?『where the cross river traffic is supposed to be built 』状语从句?is the heaviest.主从?

at which the bridge is supposed to be built 做定语修饰the place.where the cross river traffic is the heaviest做表语从句.