It is time the authorities concerned took proper steps to solve the traffic problems.有语法错误吗

题目

It is time the authorities concerned took proper steps to solve the traffic problems.有语法错误吗
“该是……的时候了”句型,请问这句子正确吗?为什么“concerned”后面的“take”还要用过去分词形式?

答案

语法完全正确
it is time 后面的句子要用虚拟的,前面用一般现在时态,后面就用过去took,或者should take
到了有关当局采取有效措施解决交通问题的时候了.
concerned ...这里是过去分词短语做定语,修饰前面的authorities