Answer:
im going to say c
Explanation:
if its has 160 units and goes to half-life after 2 months im assuming it loses 1/2 of the units so in order for it to lose that many it will have to lose 40 units a month so i say its c after 10 months there will be less than 1 unit in the potion
hope this helps im sorry if im wrong have a blessed day :)