According to the text, the cost increase in the rail industry is mainly caused by ______.

A．who work as coordinators
B．who function as judges
C．who supervise transactions
D．who determine the price

A．shippers will be charged less without a rival railroad
B．there will soon be only one railroad company nationwide
C．overcharged shippers are unlikely to appeal for rate relief
D．a government board ensures fair play in railway business