题目

Hamsters are lovely small animals which are similar to mice，and some people 1ike to keep them as pets．They need to eat a balanced diet，or they can become very sick．That’s why hamsters should be fed healthy foods． Most pet stores sell hamster mix．This is a combination of foods that are just right for hamsters．Some hamsters are picky eaters．They don’t eat anything they don’t like，so you have to find a hamster mix that your hamster will like．Most hamsters only eat a few tablespoons a day．You should feed them at the same time every day，or you can just keep your hamste科学研究表明，氨气在常压下就可液化为液氨，液氨可用作汽车的清洁燃料，其燃烧时的主要反应为 4NH3 + 3O2 ==== 2X + 6H2O。下列说法中不正确的是   A．氨气在常压下液化是物理变化      B．X的化学式为N2 C．液氨具有可燃性属于化学性质      D．液氨属于混合物