A test flight is dangerous because the test pilot has to （）.
A. fly his plane at a very high altitude
B. secure a safe landing in a plane crash
C. find out how to handle a plane when its engines stop working
D. fix the damaged engines during the flight
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Different from fish, dolphins （）
A. live on land
B. breathe with lungs
C. breathe under water
D. live without oxygen
On which day is Halloween celebrated each year（）
A. The second Sunday in May.
B. The fourth Thursday in November.
C. February 14.
D. October31.
It can be inferred that during the test, （）.
A. water is pumped into the plane instead of air
B. more air is pumped into the plane than usual
C. water exerts great pressure on the skin of the plane
D. the weaker parts receive greater pressure
6（）
A. realistic
B. effective
C. efficient
D. practical
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