Sediment is deposited as a river enters a lake because the
(1) velocity of the river decreases
(2) force of gravity decreases
(3) volume of water increases
(4) slope of the river increases

I believe that the answer is number 1. Sediment is deposited as a river enters a lake because the velocity (speed) of the river decreases - the same reason that sediment gets deposited on a river's meander.

Hope this helps! :)

The answer to the question is gold