单项选择题

A．Because their environment is becoming more and more dirty.
B．Because the traditional ways of treating wastes are not efficient.
C．Because they are short of useful materials.
D．Because they need new materials made from garbage.
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单项选择题
A．People can learn to recognize faces.B．People have different personalities.C．People have difficulty in describing the features of fingerprints.D．People differ from each other in facial features.
A．People can learn to recognize faces.
B．People have different personalities.
C．People have difficulty in describing the features of fingerprints.
D．People differ from each other in facial features.
单项选择题
A．They usually leave their children alone.B．They allow for failure on the part of their children.C．They control their children to a minimum degree.D．They set very high standards for their children.
A．They usually leave their children alone.
B．They allow for failure on the part of their children.
C．They control their children to a minimum degree.
D．They set very high standards for their children.
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