Is the answer (A) ?
$\begin{bmatrix} u1 &u2 &u3 \end{bmatrix} \begin{bmatrix} a1 &a2 &a3 \\ a4&a5 &a6 \\ a7& a8 & a9 \end{bmatrix} \begin{bmatrix} u1\\ u2\\ u3 \end{bmatrix}$
$(u1a1 + u2a4 + u3a7)*u1 + (u1a2 + u2a5 + u3a8)*u2 + (u1a3 + u2a6 + u3a9)*u3 = 0$
$u1^{2}a1 + u1u2(a4 + a2) + u1u3(a7 + a3) + u2^{2}a5 + u2u3(a8 + a6) + u3^{2}a9 = 0$
This can only be possible when the matrix A is skew symmetric. Because all the diagonal elements $(a1,a5,a9)$ will be 0. And all the non diagonal elements will be negation of each other.$(a2 = -a4, a3= -a7, a6 = -a8)$