VI. 閱讀測驗     Ships are the lifeline of trade among countries. Almost everything, from food to machinery, comes by way of the sea in huge ships piloted by captains. But the captain of a ship is responsible for guiding the vessel until they hit a port, waiting to enter the harbor. The task of bringing the ship into the harbor and anchoring it is taken up by a different captain. This captain is called a marine pilot.    A marine pilot is a boat pilot with specialized knowledge of a particular port or harbor. The pilot is needed to direct large ships into a port, where there are often deep water channels surrounded by shallower seabeds. Without the services of a marine pilot, docking ships would be hazardous. There would be a real chance of running aground and damaging the ship and the cargo, some of which might be dangerous if released into a water-based ecosystem.     In addition to the shallower seabeds, tide and wind pose further challenges for bringing ships into a port. During different tides, currents may change from one direction to the other. The same strategy for docking a vessel during an incoming tide may not work during an outgoing tide. Also, the wind can significantly alter the direction of the ship and how it reacts, adding to the difficulty of anchoring the ship.    Marine pilotage is a job that requires a high degree of proficiency as well as quick and independent thinking. Above all, it is about risk management. A marine pilot goes on board at a crucial time and controls the vessel based on his or her knowledge of the port and the situation at hand. The pilot is responsible for not only the safety of the ship but also the protection of the port and the marine environment.
【題組】46.What is the passage mainly about?
(A) A special profession.
(B) Shipping and trading.
(C) Guidelines for safe docking.
(D) Protection of the marine environment.