A．Employment in the fishing and whaling industries.
B．Nineteenth-century sea captains.
C．The economic importance of sailing ships.
D．The development of the steamship.

A．They were protected by a strong United States Navy.
B．They were supported by a well-developed railroad
C．Most crew members had experience on foreign ships.
D．As part owners of the ships, captains got some of the profits.

A．They carried passengers but not cargo.
B．They were large, but surprisingly fast.
C．They were the first successful steam-powered ships.
D．They were more reliable than other ships of the 1860's.