Answer:
B, when x approaches negative infinity B(x) approaches positive infinity and when x approaches positive infinity B(x) approaches positive infinity.
Explanation:
B(x) is a quadratic function, so B(x) will have the same end behavior for both x-> +infinity and x-> -infinity. If we multiply (3-x)(6-x), the negative x's become a positive x^2 because it is a double negative. This means that the parabola opens upwards and the end behavior of B(x) approaches positive infinity in both directions.
Attached is a snip of a Desmos graph of the problem, just in case it helps to see it.