Qualitative and quantitative momentum problems. why is it difficult for a firefighter to hold a hose that ejects large amounts of high speed water ?

the reaction force is large.

Explanation:

From Newton's third law, we know that for every action, there is equal and opposite reaction.

Since, a large amount of high speed of water is ejecting out from hose. The high momentum due to large speed in short duration of time would cause water to eject out with great force. The reaction force would act on the firefighter holding the hose. An equal amount of large force would act on him. Thus, it is difficult for a firefighter to hold a hose that ejects large amounts of high speed water.

it is the second option.