The answer to this question is A- evaporation
so you can see those fluorine atoms have really spread out around the central phosphorus atom. this gives us a trigonal bi-pyramidal molecular geometry for pf5.
The order of the answers are as follows:
B
C
D
A
C. a burning candle
all the other choices are physical changes
2.
The reason why is because there are 2 available electron spots on the orbital for the oxygen atom. Hydrogen atoms have one proton and one electron, thus, in order to fill the oxygen atom orbital to a full outer shell, a maximum of 2 atoms could bond with the oxygen atoms.
6 electrons (oxygen)+ 1 electron (hydrogen)+ 1 electron (hydrogen)= 8