A characteristic group of symptoms and signs that accompanies a disease is called a _________. Some complex disorders even have “__________” in their names. Such as Down _________, acquired immunodeficiency ___________(AIDS).
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An inadequate diet may result in ____________, on the contrary, and an adequate diet may result in___________, both of the two ailment could be________ (outcome is dead).
一个基元反应,正反应的活化能是逆反应活化能的2倍,反应时吸热 120 kJ·mol-1,则正反应的活化能是( )
A. 120 ;
B. 240 ;
C. 360 ;
D. 60 。
11. 在夫琅禾费单缝衍射实验中,欲使中央亮纹宽度增加,可采取的方法是[ ]
A. 换用长焦距的透镜
B. 换用波长较短的入射光
C. 增大单缝宽度
D. 将实验装置浸入水中
10. 无线电波能绕过建筑物,而可见光波不能绕过建筑物。这是因为[ ]
A. 无线电波是电磁波
B. 光是直线传播的
C. 无线电波是球面波
D. 光波的波长比无线电波的波长小得多