Which of the following is a valid application of the distributive property?

A. $\displaystyle{3}\cdot{\left({4}\cdot{5}\right)}={\left({3}\cdot{4}\right)}\cdot{\left({3}\cdot{5}\right)}\usepackage{cmbright}\Huge\$

B. $\displaystyle{3}\cdot{\left({4}+{5}\right)}={\left({3}\cdot{4}\right)}+{\left({3}\cdot{5}\right)}\usepackage{cmbright}\Huge\$