Select the Venn diagram that best illustrates the relationship among the following classes.
Train, Aeroplane, Scooter

Given: Train, Aeroplane, Scooter

On the basis of the relationship of the given word, The correct Venn diagram will  be:

Train operates on tracks.

Aeroplane operates in the air.
Scooter is a road-based vehicle.

So, there will be no overlapping.

Thus, the correct option is (a).