Explanation:

- You are given that P and Q divide the straight line XY into three equal parts. Hence, XQ is two-thirds of XY and YQ is one-third of XY.

- The time taken by the boat from X to Q and Y to Q is in the ratio of 4:5.

- Boats travel faster downstream because the river current aids their speed.

- Let's denote the speed of the boat in still water as B and the speed of the river current as R.

- The effective speed of the boat downstream from X to Q is \(B + R\).

- The effective speed of the boat against the current from Y to Q is \(B - R\).

- If the downstream to upstream time ratio for differential distances shows 4:5, solve using the speed relationships to find the downstream to current speed ratio.

- The correct ratio for the speed of the boat downstream to the speed of the river current comes out to be 10:3.

Therefore, Option 2: 10:3 is the correct choice.