Which of the Following Is the Best Mathematical Expression to Represent

Which of the following is the best mathematical expression to represent the fact that the pressure of a gas (P) ,at constant volume and temperature,is directly proportional to the mass of that gas (m) ?

A) P $\infty$ m
B) P = m
C) P $\equiv$ m
D) P $\approx$ m
E) P $\in$ m