Your New Weed-Cutter Requires, as Fuel, a Gas-To-Oil Mixture of 20-To-1

Multiple Choice

Your new weed-cutter requires, as fuel, a gas-to-oil mixture of 20-to-1 (20 parts of gas mixed with one part of oil) . You have 1/2 of a gallon of gas. How much oil, in gallons, should you add to make it all into fuel for the weed-cutter?

A) 2
B) 1/2
C) 1/20
D) 1/40