5. The number of $n$ that makes each interior angle of a regular $n$-sided polygon an even number of degrees is ( ).
(A) 15
(B) 16
(C) 17
(D) 18
5. (B).

For a regular $n$-sided polygon, each interior angle is $\frac{(n-2) 180^{\circ}}{n}=180^{\circ}-\left(\frac{2^{3} \times 3^{2} \times 5}{n}\right)^{0} .2^{3} \times 3^{2} \times 5$ has $(1+3)(1+2)(1+1)=24$ divisors, but $n \geqslant 3$, so we should remove $1$ and $2$, which leaves 22. When $\frac{2^{3} \times 3^{2} \times 5}{n}$ is odd, $n$ is a multiple of $2^{3}$ and a divisor of $3^{2} \times 5$, which gives $(1+2)(1+1)=6$ possibilities. Therefore, $n$ has 16 possibilities.