What does the passage mainly discuss()
A. The history of surveys in North America
B. The principles of conducting surveys
C. Problems associated with interpreting surveys
D. The importance of polls in American political life
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Titanium has the (strength) of steel but weighs (half only) as much, hence its (advantage) for use (in aircraft).()
A. strength
B. half only
C. advantage
D. in aircraft
The word "these" in line 20 refers to()
A. golden eagles
B. generations
C. winds
D. nests
The (poor )condition of (prisoners are ) what (concerned) Dorothea Dix, an American social worker and (director of) a school ill Boston.()
A. poor
B. prisoners are
C. concerned
D. director of
The brain of an average adult is one of the largest organs of the body()about three pounds.
A. weighs
B. is weighed
C. weighing
D. to weigh it