[单项选择]Merchant and passenger ships are generally required to have a life preserver for every person aboard and, in many cases, a certain percentage of smaller sizes for children. According to United States Coast Guard requirements, life preservers must be simple in design, reversible, capable of being quickly adjusted to fit the uninitiated individual, and must be so designed as to support the wearer in the water in an upright or slightly backward position.
Sufficient buoyancy to support the wearer should be retained by the life preserver after 48 hours in the water, and it should be reliable even after long period of storage. Thus it should be made of materials resistant to sunlight, gasoline and oils, and it should be not easily set on fire.
The position in which the life preserver will support a person who jumps or falls into the water is most important, as is its tendency to turn the wearer in the water from a face-down position to an upright or slightly backward position, with
A. the uses of life preserver
B. the design of life preserver
C. the materials for life preserver
D. the buoyancy of life preserver

[单项选择]Merchant and passenger ships are generally required to have a life preserver for every person aboard and, in many cases, a certain percentage of smaller sizes for children. According to United States Coast Guard requirements, life preservers must be simple in design, reversible, capable of being quickly adjusted to fit the uninitiated individual, and must be so designed as to support the wearer in the water in an upright or slightly backward position.
Sufficient buoyancy to support the wearer should be retained by the life preserver after 48 hours in the water, and it should be reliable even after long period of storage. Thus it should be made of materials resistant to sunlight, gasoline and oils, and it should be not easily set on fire.
The position in which the life preserver will support a person who jumps or falls into the water is most important, as is its tendency to turn the wearer in the water from a face-down position to an upright or slightly backward position, with
A. adjustable
B. comfortable
C. self-evident
D. self-righting

[单项选择]Passenger ships and ______ are often equipped with ship-to-shore or air-to-land radio telephones.
A. aircrafts
B. aircraft
C. the planes
D. also the planes

[单项选择]
Clipper ships are small, lightweight vessels with three masts that boast a massive array of sails which allow them to move extremely quickly. The name "clipper" is thought to come from the fact that the bow of such a ship seems to cut through water as it advances, something also true of older types of ship. Certainly, people were using the expression "to go at a good clip" to mean "to travel quickly" long before the advent of the clipper ship, so the explanation seems to make sense. In fact, it is difficult to date the emergence of the first true clipper, since the word was liberally applied to several speedy ships from the early 19th century that did not possess the technical specifications to qualify as clippers under the later definition of the term. What is known, however, is that by the 1840s, several shipyards were engaged in building vessels that were recognizably clipper ships.
The great advantage of the clipper
A. The great speed at which the ship moves.
B. The way the ship cuts through the water.
C. The fact that the ship clips time off the trip.
D. The use of the word in an early newspaper edition.

[单项选择]Which graph shows the airline~s passenger volume