Answer
4
Work Step by Step
When the terms are written in order, the polynomial can be written as:
$$-a^4+2a^3+9a+3$$
Thus, in order, we see that (a) the degree of each term is 4, 3, 1, 0; (b) the leading term is $-a^4$ with a coefficient of -1; and (c) the degree of the polynomial is 4.