In the figure, the value of $ a$ is:
Step 1: Calculate the value of
As we know, the angles on the same sides of a straight line formed on the same point are supplementary.
Now, since is a straight line.
So,
Step 2: Calculate the value of
As we know, the vertically opposite angles formed by intersection of two straight lines are equal.
Then, since and are straight lines intersecting at point .
So,
Hence, , so option D is the correct option.