Blimps and hot air balloons are very different from each other. A balloon has to go wherever the wind takes it, whereas a blimp is (a)   by its two engines.

Blimps offer television viewers a bird's-eye view of sporting events. They can remain (a)   above the staidum for as long as necessary.

Companies with something to advertise like blimps. They offer a (a)   way of showing off the company's message to the people below.

Blimps are used to take air samples at different heights. The purpose of this is to see how much the air is being (a)   by natural and human causes.

Blimps are not useful as weapons of war. They are so big and slow moving that they would be unable to (a)   an enemy attack.

The blimp's air bag is filled with helium. Once the bag has been (a)   the helium stays inside until major repairs are needed.

Hydrogen is an even lighter gas than helium. It is not used in blimps because it is highly (a)   .

A blimp stays on the ground except during calm weather. Because it is ligher than air, it is easily (a)   by strong winds.

A blimps usually stays outside while on the ground. It swings from its (a)   so that it always faces into the wind.

A blimp needs plenty of space around it while on the ground. It has to be free to (a)   all the way around in a full circle.

A blimp's pilot keeps a close watch on weather patterns. He will not take it (a)   if strong winds are expected.

Blimp pilots like to fly low. Although blimps can (a)   much higher altitudes, pilots usually fly just a few hundred feet above the ground.

A blimp pilot's first concern is the well-being of the passengers. The pilot will not do anything that might (a)   their safety.

Most people feel quite safe in the gondola of a blimp. The only way it would (a)   to the ground is if it iseparated from the envelope above.