Answer:B) a reactant that undergoes reduction
Explanation:
Oxidation reaction is defined as the reaction in which a substance looses electrons. The oxidation state of the substance increases during oxidation.
Reduction reaction is defined as the reaction in which a substance gains electrons. The oxidation state of the substance gets reduced during reduction.

Overall reaction: 
The substance M which itself gets oxidized, reduces other and is called as reducing agent. The substance N which itself gets reduced, oxidizes other and is called as oxidizing agent.
<span>PV/T = P'V'/T'
660 x 1.00/295.2 = P' x 1.00/317.8
P'=710.5 torr</span>
I believe this pertains to chemical reaction? So my guess would be answer A “Fire burning”
Don’t quote me though lol.