12．In the United States，30 percent of the people have a"weight problem"．To many people the cause is obvious（明显的）：They eat too much．But scientific evidence does little to support this idea．Going back to America of 1910，we find that people were thinner than today，yet they ate more food．In those days people worked harder physically，walked more，used machines much less，and didn't watch television．
Several modern studies，moreover，have shown that fatter people don't eat more on average than thinner people．A 1979 study of 3，545 London office workers shows that fat people eat less than slim（苗条的）people．
Studies also show that slim people are more active than fat people．A study by a research group at Stanford University found the following interesting facts：The more the man ran，the greater loss of the body fat．The more they ran，the greater increase in food intake．
Thus，those who ran the most ate the most，yet lost the greatest amount of body fat．
32．Nowadays many Americans have the problem thatC．
A．they are too slim
B．they work too hard
C．they are too fat
D．they lose too much body fat
33．According to the passage，how many people in 900 Americans have a"weight problem"？D
A.150．B.300．C.600．D.270．
34．Is there any scientific evidence to support the idea that eating too much is the cause of a"weight problem"？C
A．Yes，there is plenty of evidence．
B．Of course，there is some evidence to support this．
C．There is hardly any scientific evidence to support this．
D．We are not sure．
35．The Americans in 1910A．
A．ate more food and had more physical activities
B．ate less food but had more physical activities
C．ate less food and had less physical activities
D．had more problems．
