Option B: 2 : 7
For $5x^2 - 6x + 21 = 0$: Sum of roots $= \frac{6}{5}$, Product of roots $= \frac{21}{5}$.
Ratio = $\frac{6}{5} : \frac{21}{5} = 6 : 21 = 2 : 7$.
Using Vieta's formulas: sum of roots $= -b/a = 6/5$ and product of roots $= c/a = 21/5$. Dividing both by $1/5$ gives ratio $6:21$, which simplifies to $2:7$. Examiners expect you to recall these formulas directly from the chapter on quadratic equations.