Which of the following is NOT an example of reflex action by our nerv…

The correct answer is Option (4) → Raju smells smoke in his house and runs out of home to save himself.

A reflex action is a sudden, automatic response to a stimulus, made without thinking or deciding. The message from the sense organ goes to the spinal cord (or a lower part of the brain), and the response comes back at once along the reflex arc.

Option (1) On seeing her sweet dish, Puja has water in her mouth. — A reflex action (Incorrect). Saliva flows on its own at the sight of food we like; Puja does not decide to make her mouth water.

Option (2) Ravi touches a hot plate, and immediately removes his hand from the plate. — A reflex action (Incorrect). Pulling the hand away from heat is the withdrawal reflex, controlled by the spinal cord before the pain is even felt.

Option (3) Rakesh touches an icy cold glass and immediately removes his hand. — A reflex action (Incorrect). It is the same withdrawal reflex, set off by extreme cold instead of heat.

Option (4) Raju smells smoke in his house and runs out of home to save himself. — Not a reflex action (Correct). Raju has to recognise the smell as a sign of fire and decide to run out. This thinking is done by the brain, so it is a voluntary action, not an automatic reflex.