Answer:
A
Step-by-step explanation:
The measure of angle D can be found using the Interior Angle Sum of a Triangle.
The angles of a triangle add to 180. This means:
90 + 21 + x = 180.
111 + x = 180
x = 69
The solution is A.
Angle B is smaller than Angle D which means CD will be smaller than BC.
Not sure why such an old question is showing up on my feed...
Anyway, let

and

. Then we want to find the exact value of

.
Use the angle difference identity:

and right away we find

. By the Pythagorean theorem, we also find

. (Actually, this could potentially be negative, but let's assume all angles are in the first quadrant for convenience.)
Meanwhile, if

, then (by Pythagorean theorem)

, so

. And from this,

.
So,
B....................................................