题目

阅读下列短文，从下题所给的A、B、C、D四个选项中选出最佳选项。Although midnight snacks or being too tired to exercise could make people get fatter, there may now be a more scientific reason. A study has shown short or restless sleep changes the way people's DNA works and makes the body store fat. Fat stores begin to rise when people lose as little as one night's sleep, the researchers found.Sleep researchers from Uppsala University in Sweden did a study on people after two lab tests—in one they slept for over eight hours and in the other they did not sleep at all. R运输食品用干冰(固态二氧化碳)保鲜，是由于干冰 [　　] A．蒸发时要吸热 B．升华时要吸热 C．汽化时要放热 D．升华时要放热