Question

fireman holds the hosepipe tightly. give reason

Answer 1

to not get flown away by that force and also to to not change the direction of water on fire

Answer 2

Fireman holds the hosepipe tightly.

REASON:
According to Newton's Third Law of motion " For every action there is equal and opposite reaction"
ACTION FORCE = -REACTION FORCE

Large amount of water is ejected with a large force in forward direction ( action force).
Reaction force will be in backward direction which the fire man experiences.
So he feels it difficult to hold the hose.