First Principles Thinking: productivity per unit of selling space
B is correct. Sales per square meter equals revenue divided by total retail space. Dividing USD 20,000,000 by 2,000 square meters gives USD 10,000 per square meter.
A results from dividing by 20,000 square meters, which is not given.
C results from dividing by 200 square meters, inconsistent with the stated 2,000.