Answer:
Liquid to solid liquid to gas
Explanation:
Boiling a liquid result in a gas
Each correspond to a principal energy level
STP stands for standard temperature and pressure. Standard pressure is equivalent to 1 atm, and standard temperature is equivalent to 273.15 K. Therefore, your answer is A. the temperature is 273.15 kelvin.
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D. 1 proton and 1 neutron