What Is the Appropriate Order of Stages Needed to Investigate $\circ$

What is the appropriate order of stages needed to investigate whether maple trees drop their leaves in the autumn because of colder days?
(1) Maple trees are grown in 2 greenhouses where the only variable is temperature (15 ^$\circ$ C vs.10 ^$\circ$ C) .
(2) The hypothesis is rejected.
(3) There is no statistical difference in the number of leaves dropped at 10 ^$\circ$ C as compared to 15 ^$\circ$ C.
(4) The observation is that maple trees drop their leaves in autumn.
(5) The hypothesis is that maple trees drop their leaves because of colder temperatures.

A) 1,2,3,4,5
B) 3,4,5,1,2
C) 5,4,3,1,2
D) 4,5,1,3,2
E) 3,4,2,1,5