Which half-reaction goes first in a REDOX process?

Don't think it matters.

Explanation:

In terms of classifying them, find the oxidation numbers first. Reduction half-reaction will gain electrons, so oxidation number will decrease across. Oxidation half-reaction will lose electrons, so oxidation number will increase across.

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.  

the answer would be b i believe