Answer:
A
Step-by-step explanation:
Can't be B, because for people who burn less than 2000 calories a day, eating 2000 calories would cause the them to gain weight. (Small people who don't move around much burn less than 2000 calories a day.)
Probably not C, unless the source points out that fact. This source has a mission to be clear in presenting to the public, so unless they point out the fact implied, it's unlikely to be their motivation.