B. If the equation about $x$
$x^{2}-p x-q=0$ ( $p, q$ are positive integers)
has a positive root less than 3, then the number of such equations is ( ).
(A) 5
(B) 6
(C) 7
(D) 8
B. C.

From the relationship between the roots and coefficients of a quadratic equation, we know that the product of the two roots is $-q0$.
Therefore, $3^{2}-3 p-q>0 \Rightarrow 3 p+q<9$.
Since $p, q$ are both positive integers, we have $p=1,1 \leqslant q \leqslant 5$; or $p=2,1 \leqslant q \leqslant 2$.
Thus, there are 7 pairs of $(p, q)$ that satisfy the condition.