Odd one out

There is a bird, plane, a square with a hole and a cloud, which one does not fit?

The purpose of this problem is to highlight that explanations are as important as answers themselves. In fact, any object can be singled out:

• the bird, because it's the only animal;
• the plane, because it's the only mechanical object;
• the square, because it's abstract, or because it does not fly;
• the cloud, because it's gas/liquid (immaterial, but not abstract).

Odd one out

There is a bird, a plane, a square with a hole and a cloud, which one does not fit?

The purpose of this problem is to highlight that explanations are as important as answers. In fact, any object can be singled out:

• the bird, because it's the only animal;
• the plane, because it's the only mechanical object;
• the square, because it's abstract, or because it does not fly;
• the cloud, because it's gas/liquid (immaterial, but not abstract).