Answer:
The measure of chord CD is 5 units
Explanation:
As 
we have given two triangles that are congruent 
and 
we know that the two congruent triangles are congruent they will have exactly the same three sides and exactly the same three angles and also the equal sides and angles may not be in the same position so 
from the definition we say that the 
Measure of chord CD is same as AB 
so Correct option is D that is 5 units.