The Coefficient of Cubical Expansion Is Related to the Coefficient $\beta$

The coefficient of cubical expansion is related to the coefficient of linear expansion by the expression

A) $\beta$$\approx$$\alpha$ .
B) $\beta$$\approx$ 2 $\alpha$ .
C) $\beta$$\approx$ 3 $\alpha$
D) $\beta$$\approx$ 4 $\alpha$ .