Answer:
Part 1: 193.33 meters
Part 2: A and D
Explanation:
We are given that,
Height of the taller building 'A' = 207 meter
Distance between both the buildings = 51 meter
Angle of depression from the top of the taller building to the top of the smaller building = 15°
Since, we know that, 'The angle of depression is equal to the angle of elevation'
We get the figure below for the situation.
Part 1: To find the height of the smaller building.
Using trigonometric form for the angles in right triangles, we get,

i.e.

i.e.

i.e. x= 13.67 meters.
So, the height of the smaller building 'y' = 207 - 13.67 = 193.33 meters
Hence, the height of the smaller building is 193.33 meters
Part 2: Relation between the angle of depression and the angle of elevation.
Since, both the angles are made when a transversal intersects two parallel lines.
And, 'when the transversal intersects two parallel lines, the alternate interior angles are same'.
So, we have that, the correct options for the angle of depression and the angle of elevation are:
A. They are congruent
D. They are alternate interior angles.