5. If $a+b+c=a b c, A=\frac{\left(1-b^{2}\right)\left(1-c^{2}\right)}{b c}+$ $\frac{\left(1-a^{2}\right)\left(1-c^{2}\right)}{a c}+\frac{\left(1-a^{2}\right)\left(1-b^{2}\right)}{a b}$, then the value of $\mathrm{A}$ is
(A) 3
(B) -3
(C) 4
(D) -4
$\begin{array}{l}\text { 5. (C). } \\ \text { Let } a=\tan \alpha, b=\tan \beta, c=\tan \gamma. \text { Then } \\ \tan \alpha+\tan \beta+\tan \gamma=\tan \alpha \cdot \tan \beta \cdot \tan \gamma, \\ \text { and } A=4(\cot 2 \beta \cdot \cot 2 \gamma+\cos 2 \alpha \cdot \cot 2 \gamma \\ \quad+\cot 2 \alpha \cdot \cot 2 \beta)=4 .\end{array}$