听力原文： The number of job opportunities for pilots in the U. S. is expected to grow abou

t as fast as the average of overall employment growth from 2003 to 2010. However, competition for jobs will continue to be high. Causes that slow growth are a function of mergers and challenges in the airline industry. In addition, advancements in technology reduce the need for Flight Engineers, and video conferencing and teleconferencing reduce the need for business travel. Some industry analysts predict the need for 27,000 new pilots between 2003 and 2010 as a result of retirement. Many of the pilots who were hired in the 1960s are now reaching mandatory retirement age, and thus a few thousand job vacancies are expected to arise each year for the next several years. Note that not many pilots retire early because of the high earnings and benefits, and the fact that their unique skills are not generally transferable to other careers. The employment of pilots is sensitive to changes in the economy. Airlines are forced to furlough or temporarily lay-all pilots during periods when the demand for air travel declines. At times of recession, pilots employed in commercial or corporate flying and flight instruction are adversely affected by the downturn in the economy.

What is the caravan？

A．A kind of business.

B．A group of people who travel together.

C．A means of transportation.

D．A marketplace.