3. Let $a, b, c, d$ be real numbers, and suppose that all the roots of the equation $z^{4}+a z^{3}+b z^{2}+c z+d=0$ lie on the circle with center at the origin and radius 1 in the complex plane, then the sum of the reciprocals of these roots must be
A. $a$
B. $b$
C. $c$
D. $-a$
3. $\mathrm{D} \sum \frac{1}{z_{1}}=\overline{z_{1}}+\overline{z_{2}}+\overline{z_{3}}+\overline{z_{4}}+\overline{z_{5}}=\overline{-a}=-a$