P represents heating and Q represent cooling.
this is because when you start from a liquid and turn to a gas the particles move faster making them farther apart, causing a gas. the opposite happens when you go from a liquid to a solid. the partials move closer together causing a solid to form. :)
I would choose answer 2, since that answer is based on a same size consisting of more than 1 person, making it applicable to statistic analysis and have an input in the observational study. The other questions ask for one data point, which isn't statistical
Source: AP Statistics
Explanation is in the file
tinyurl.com/wtjfavyw
A is the answer correct answer hope I helped