5. The set $A=\left\{z \mid z^{18}=1\right\}, B=\left\{w \mid w^{48}=1\right\}$ are both sets of complex roots of 1, and the set $C=\{z w \mid$ $z \in A, w \in B\}$ is also a set of complex roots of 1. The number of distinct elements in set $C$ is ( ).
A. 144
B. 66
C. 6
D. 864
5. A $(z \omega)^{144}=1$ (144 is the least common multiple of 48 and 18)

Since $e^{\frac{2 k \pi}{144}} i=\left(e^{\frac{2 \pi}{18} i}\right)^{3 k} \cdot\left(e^{\frac{2 \pi}{18} i}\right)^{-k}$
Therefore, $C$ contains 144 elements