D both are right triangles
Decreasing then increasing, y goes down then y goes back up
Answer:

Step-by-step explanation:
It is a linear homogeneous differential equation with constant coefficients:
y" + 4y = 0
Its characteristic equation:
r^2+4=0
r1=2i
r2=-2i
We use these roots in order to find the general solution:

I believe that A and D would be the correct answer. Because both are 30,60,90 triangles and would be congruent. The other 2 triangles only have 1 angle and their side measures are at two different places meaning they cannot be congruent.