题目

  I’ve often wondered how exactly sleep, or lack of it, can have such an awful effect on our bodies and, guess what, how much we sleep switches good genes(基因) on and had genes off.   In the first half of 2013, the Sleep Research Centre at the University of Surrey found a direct link between hours spent sleeping and genes. Every cell in our bodies carries genetic instructions in our DNA that act as a kind of operating handbook. However, each cell only “reads” the part of this handbook it needs at any given moment.     Can sleep affect how a gene reads instructions? It’s 7．下列属于物理变化的是（　　）A．用鲜牛奶和乳酸菌制酸牛奶B．用糯米等原料做甜酒酿C．用彩纸折幸运星D．纸张燃烧