A recipe asks that the following three ingredients be mixed together as follows: add 1/2 of a cup of flour for every 1/2 of a teaspoon of baking soda, and every 1/4 of a teaspoon of salt. Which of the following rates is a unit rate equivalent to the ratios shown above?

A. 2 teaspoons of salt per 1 cup of flour

B. 1/2 teaspoon of salt per 1 teaspoon of baking soda

C .2 teaspoons of salt per 1 teaspoon of baking soda

D. 1 teaspoon of baking soda per 2 teaspoons of salt