Answer:
Option C) 15
Explanation:
It is given that CD is perpendicular bisector of both XY and ST and CY = 20
We have to find the measure of CT.
In the triangles CSM and CTM
SM = MT = 7 (CD is perpendicular bisector of ST)
∠ CMS = ∠ CMT = 90°
Side CM is common in both the triangles.
So, Δ CSM ≅ Δ CTM
Therefore, side CS = side CT = 15
Option C) 15 is the correct option.