1) The answer is (D)

On each side, there can be a maximum of 13 trees: one at the beginning and 12 more spaced $15 \mathrm{~m}$ apart from each other. The last one will thus be exactly at the end of the avenue.
1) How many trees can be placed at most on both sides of a wide avenue that is 180 meters long, placed 15 meters apart from each other?
(A) 20
(B) 22
(C) 24
(D) 26
(E) 28.