it is hard to be in a crowded bus on commuting.其中去掉to be可以吗 为什么要加 to be

问题描述:

it is hard to be in a crowded bus on commuting.其中去掉to be可以吗 为什么要加 to be

不能去掉.
in a crowded bus ,可以先忽略不计.就是it's hard to be on commuting.
句型 it is hard to do sth /to be ...