Mrs. Khan makes cookies for the school bake sale. She uses the equation c = 0.75x to determine the cost, c, for x cookies. Which best represents the constant rate at which cookies are sold at the bake sale?

This is a rational expression because the denominator contains a variable. this is a polynomial with 3 terms. this is a rational expression because the denominator contains a variable. this is a polynomial with 4 terms. this is a rational expression because the denominator contains a variable. this is a polynomial with 4 terms. this is a rational expression because the denominator contains a variable. this is a polynomial with 3 terms. this is a rational expression because the denominator contains a variable. this is a polynomial with 5 terms.