Explanation:

- The toy's total volume consists of three parts: the cylinder, the cone, and the hemisphere.

- The cylinder's contribution is 50% of the total volume.

- The cone's contribution is 20% of the total volume.

- This means the hemisphere's contribution is the remainder, which is 30%.

- We need to find the ratio of the contributions of the cone, cylinder, and hemisphere.

Let's break it down:

- Cone: 20%

- Cylinder: 50%

- Hemisphere: 30%

- To find the ratio, divide each percentage by the common factor in such a way that it simplifies to whole numbers.

- This gives us a ratio of 20:50:30.

- Simplifying further by dividing each by 10, we get 2:5:3.

Therefore, the correct option is 2: 5: 3.

Option: 3