这是什么从句?that做什么成分?It has been estimated that if the bridge were packed with cars,it would still only be carrying a third of its total capacity.

这是什么从句?that做什么成分?It has been estimated that if the bridge were packed with cars,it would still only be carrying a third of its total capacity.
这是什么从句?that做什么成分?
It has been estimated that if the bridge were packed with cars,it would still only be carrying a third of its total capacity.

这是什么从句?that做什么成分?It has been estimated that if the bridge were packed with cars,it would still only be carrying a third of its total capacity.
that 引导的是主语从句,因为太长所以放在了后面,然后用it充当形式主语.正常语序应该是：
that if the bridge were packed with cars,it would still only be carrying a third of its total capacity has been estimated.

主语从句 It是形式主语 that从句是真正的主语

主语从句

主语从句。that作连接代词。

主语从句， that 不做成分

that 引导的是主语从句，因为太长所以放在了后面，然后用it充当形式主语。正常语序应该是：
that if the bridge were packed with cars, it would still only be carrying a third of its total capacity has been estimated.

宾语从句，that就是个引导词，不做成分~