单项选择题 When comparing the air with 50% of relative humidity with the air with 100% of relative humidity, which one will hold more water?（）

单项选择题 What is the result of converting 10℃ into degree of Fahrenheit?（）

单项选择题 A process of comparing the actual performance of a machine with the intended performance, and the adjusting the machine to reduce and eventually eliminate the difference between the actual and intended performance is called（）