The man fed the girl. (Change into Passive Voice)

The editor was editing an important news. The passive form of this sentence is :

He will certainly help the poor boy (Change into passive voice) :

The workers built a bridge. (change into passive voice)

In the following question, a sentence has been given in Active/Passive Voice. Out of the four alternatives suggested, select the one which best expresses the same sentence in Passive/Active Voice.

Grid failure brings five hundred trains to a halt.

Which sentence cannot be changed into passive voice