在水模体内，射野大小30cm×30cm，其等剂量曲线特点是（）
A.对于60Coγ射线，任何深度处等剂量由线射线中心轴上的值都是最小的，随着向射野边界靠近而增加
B.对于60Coγ射线，任何深度处等剂量曲线射线中心轴上的值都是最小的，随着向射野边界靠近而减少
C.对于兆伏级光子线，在浅层深度处，同一深度的离轴剂量通常比中心轴剂量大，这是由于均整块的设计所导致的
D.对于兆伏级光子线，在浅层深度处，同一深度的离轴剂量通常比中心轴剂量大，这是由于散射箔的设计所导致的
E.对于兆伏级光子线，在浅层深度处，同一深度的离轴剂量通常比中心轴剂量大，这是由于光子线的靶设计所导致的
参考答案：C
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| A cold is a common (普通的) illness. It often starts with a sore 1 . You sneeze (打喷嚏) and your nose runs. You usually 2 a fever, too. It's not a serious illness', but you can feel very 3 . What should you do when you have a cold? You should have a good rest. It is good 4 a lot of water, too. You can 5 and take some medicine. Maybe you can try some Chinese medicine. Chinese medicine is now very 6 all over the world. Where does Chinese medicine 7 ? A long time ago, when people were not feeling 8 , they found that some plants could make them feel 9 . They ate the leaves, the roots (根), the fruits or the seeds (种子) of the plants. Today people make much Chinese medicine 10 those plants. | ||||
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