Determine the Equation That Expresses the Statement $F$ Is Directly Proportional To

Multiple Choice

Determine the equation that expresses the statement. $F$ is directly proportional to $x$
Symbols $a , b , c , d$ are constants.

A) $F = c x ^ { 3 } + d$
B) $F = c x ^ { 5 } + d$
C) $F = a$
D) $F = b$
E) $F = \alpha x$