Step 1: Recall the condition for equal roots.
For a quadratic \(ax^2 + bx + c = 0\), roots are equal when
\[
D = b^2 - 4ac = 0
\]
Step 2: Substitute values.
Here, \(a = 3, b = 5, c = -q\).
\[
b^2 - 4ac = 0 \implies 25 - 4(3)(-q) = 0
\]
Step 3: Simplify.
\[
25 + 12q = 0 \Rightarrow q = -\dfrac{25}{12}
\]
Step 4: Verify given options.
Correct answer matches option (A) $-\dfrac{25}{12}$.
(Note: If the printed options differ, the logic confirms this value.)