题目

Frank is a student who keeps the phone with him at all times. His dad thinks he is addicted （上瘾）to his phone. But Frank doesn`t think so. They write to each other.Dear Frank, You have heard the warnings. It is reported that fifty percent of the teenagers depend on their phones too much. I think you have this problem too. I am warned that you are developing some bad habits. You keep your phone with you all the time-- you even check the basketball scores at the dinner table. It is not a good idea to use you phone while you are doing homework. And you may make more mistake when you can`t 关于晶体和非晶体，下列说法中正确的是（ ）A．晶体和非晶体都有固定的熔点B．晶体和非晶体吸收热量时都可能变成液体C．晶体和非晶体熔化时都要吸收热量且温度保持不变D．晶体和非晶体熔化时都要先变软，然后变成粘稠体，最后变成液体