After how many time train shall be protected by Guard in rear if 1st stop signal found in On position? A. 10 minutes B. 5 minutes C. 15 minutes D. No need

The correct answer is D. No need.

A train shall be protected by Guard in rear if 1st stop signal found in On position if the train is not fitted with Automatic Warning System (AWS). AWS is a train protection system that is designed to prevent trains from passing through stop signals at danger. If a train is fitted with AWS, the guard is not required to protect the train in rear.

The other options are incorrect because they do not take into account the fact that the train may be fitted with AWS.