题目

DNA在下列哪一个温度下会变性( ) A．20 ℃                     B．40 ℃ C．60 ℃                     D．100 ℃   答案：D大多数蛋白质不能忍受60～80 ℃的高温，而DNA在80 ℃以上时才会变性。It is difficult to _______ the discussion, with so much noise around us. [　　] A．carry offB．carry on C．carry awayD．carry back