"maximum constructive interference occurs at the

(1)
antinodes a, c, and e

(3)
antinodes b and d
(2)
nodes a, c, and e

(4)
nodes b and d
"

The diagram you posted above represents a standing wave on a string. The maximum constructive interference occurs at the antinodes B and D. The correct answer choice is number 3, antinodes B & D. Be careful when choosing as the above choices are not in correct order. Instead of 1,2,3,4, the choices above are 1,3,2, and 4.