Final answer:
The ratio of the areas of two round dinner plates with diameter ratios of 2:5 is 4:25.
Step-by-step explanation:
When comparing round dinner plates with a ratio of sizes 2:5, to find the ratio of their areas we should consider that the area of a circle is proportional to the square of its radius (or diameter).
If the ratio of the diameters of two plates is 2:5, we square this ratio to get the ratio of their areas because the area of a circle is π * radius^2. Therefore, the areas will be in a ratio of 2^2:5^2, which is 4:25.
The correct answer is (a) 4:25.