Correct answer choice is :
D) Companies replaced hand-operated brakes with air brakes on trains.
Step-by-step explanation:
There is a demand among railway track sustaining programmers for a better knowledge of the long-term performance of railway track operations and for advanced auspicious methods. The use of correct methods to predict railway track situations improves track protection and support effectiveness. The purpose of this analysis is to enhance current track decline modeling methods using a thorough track inquiry.