Answer: B. kilograms per month
Step-by-step explanation:
Given: Heba wants to measure the rate at which her client's muscle mass increases over time.
We know that the standard unit of mass is kilogram.
Also the increase in the muscle takes time which can be months.[ Since years is too long time period for increase in muscles.]
Also we know that time is an independent quantity and increase in mass depends on the time , therefore mass is a dependent quantity.
Therefore, the appropriate unit for Heba's purpose= kilograms per month.
