Answer:
c. 40°
Step-by-step explanation:
The information given has been illustrated in the figure drawn in the attachment below.
m<BAD = 50° (angle bisector theorem)
m<ADB = 90° (perpendicular bisector)
m<ABD = 180 - (m<BAD + m<ADB) (sum of angles in a triangle)
m<ABD = 180° - (90° + 50°)
= 180° - 140°
= 40°
B = 40°
