2021 AMC 12A Problem 13

Each listed number has modulus $2,$ so $z^5$ has modulus $32,$ and its real part is $32\cos(5\theta),$ where $\theta$ is the argument of $z.$ The arguments are $180^\circ,$ $150^\circ,$ $135^\circ,$ $120^\circ,$ and $90^\circ.$ Multiplying by $5$ gives $900^\circ \equiv 180^\circ,$ $750^\circ \equiv 30^\circ,$ $675^\circ \equiv 315^\circ,$ $600^\circ \equiv 240^\circ,$ and $450^\circ \equiv 90^\circ.$ The largest cosine is $\cos 30^\circ,$ from $z = -\sqrt3 + i,$ giving real part $16\sqrt3.$ Thus, the correct answer is B.