Context: Trichlorofluoromethane was once used in refrigerators and fire extinguishers. It is no longer used because it harms the atmosphere's ozone layer. The chemical formula for trichlorofluoromethane is CCl3F.
Complete the statement.
Trichlorofluoromethane is ().
A. a compound
B. an elementary substance
From the given choices, choose the correct answer and respond with the letter of that choice.

A