A:杯中液态氮放热
B:杯中液态氮温度不断下降
C:杯中液态氮不断吸热,温度保持﹣196℃
D:白霜是空气中水蒸气液化形成的
It was not until dark ___ he was aware of ___ he thought was the correct way to solve the problem.
铁是____的,锈是____的;