All these three elements are different from each other

Some questions are asked in examination and some in practice but examination and practice are different from each other.

Bulb and Lamp are different from each other but light is obtained from both.

All the three are different from each other.

All the three are different from each other.

Hospital consists of nurse and patient but nurse and patient are of two different nature.

Mercury and Zinc both are different from one another but belong to metal.

A teacher may or may not be a writer and musician. Similarly a musician may or may not be a teacher and writer and so a writer may or may not be a teacher and musician.