Measure of Angle 2 = 100 degrees
measure of Angle 6 = 100 degrees
Since angle 2 and angle 6 are both 100 degrees, this makes them congruent angles. They are also corresponding angles as well.
The fact we have corresponding angles that are congruent leads to AB being parallel to CD. This is using the Converse of Corresponding Angles Theorem.
Since we already know that the older child is a girl (a 100% chance to be a girl), there must be a 50% chance that the other child is a girl. Therefore, the probability that both children are girls is 50%.
Hope this helps!
Answer:
Option 1: CD is a perpendicular bisector of AB
Step-by-step explanation:
Let us find out the slopes of various line segments and the Distances and then we will draw the conclusions accordingly.
Formula to find slope

Formula to Find Distance between two points

mAB ( represents , Slope of AB )
1. 
2. 
3. 
4. 
5. 
mAC = mBC , and C is common point , hence these three are collinear points making a straight line whole slope is 



Hence CD ⊥ AB
Also
From Point 4 and point 5 above , we see that
AC = CB
Hence CD bisect AB at C, also CD ⊥ AB
There fore
CD is a perpendicular bisector of AB
Therefor option 1 is true