A2. If the expression $b c(b+c)+c a(c-a)-a b(a+b)$ is written as a product, we get
(A) $(a+1)(b+c)(c-a)$
(B) $(b+c)(c-a)(a-b)$
(C) $(c-a)(b+c)(a-b)$
(D) $(a+b)(b+c)(c-a)$
(E) none of the above
A2. The expression can be written as

$$
\begin{gathered}
b c(b+c)+c^{2} a-c a^{2}-a^{2} b-a b^{2}=b c(b+c)+a\left(c^{2}-b^{2}\right)-a^{2}(c+b) \\
=(b+c)\left(b c-a^{2}\right)+a(c-b)(c+b)=(b+c)\left(b c-a^{2}+a c-a b\right) \\
=(b+c)(b(c-a)+a(c-a))=(b+c)(c-a)(b+a)
\end{gathered}
$$

and such a product is given in answer (D).