Question

pls answer the 12th question

Answer 1

your answer is in this pic

Answer 2

let O and O' as the center of two circle 
join AB 
we know that angle in semi circle is 90 degree.
so, angle ABC = 90 degree-------------(1)
and angle ABD = 90 --------------------(2)
 adding 1 and 2
angle ABC + angle ABD = 180 degree 
therefore , CBD is a straight line.
Thus B lies on a Line segment CD. 
if you understand 

then please mark as a brainliest 
and give 5 star and thanks too.