Which of the following is the possible risk in using nano—materials mentioned in the passage？
A. They may cause some damage to the body cells．
B. They are harmful materials themselves．
C. They may store in the body．
D. They may behave differently in the body and the environment．
From the last paragraph we may infer that one of the effective measures suggested
A. not to permit them to watch TV at all．
B. to tell them to spend less time watching TV
C. to turn off TV when they are in front ff TV sets．
D. to calculate accurately the time that a child spends watching TV．
A．nutrition B．nutritions C．calorieD．calories
A. nutrition
B. nutritions
C. calorie
D. calories
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