For two lines to be parallel, their direction ratios must be proportional.
The direction ratios of the first line are \( (a, b, c) \).
The direction ratios of the second line are \( (5, 3, 2) \).
Therefore,
\[
\frac{a}{5} = \frac{b}{3} = \frac{c}{2}
\]
which implies
\[
5a = 3b = 2c
\]
Thus, the correct option is:
\[
\boxed{5a = 3b = 2c}
\]