Answer:
A. c = kn
Step-by-step explanation:
The cost c varies directly as the numbers n of pencils
This means that c is a multiplication of a constant by n, which is the number of pencils. So the equation for the cost is given by:
[tex]c = kn[/tex]
In which k is the constant of proportionality, that is, the cost of each pencil. So the correct answer is given by option A.