What is the measure of the marked angle? (photo included)

Answer:
B) 42 Degrees
Step-by-step explanation:
An angle bisector is basically a line that splits an angle into two congruent angles.
In this case, the large angle ABC is bisected by ray BD.
Angle ABC is given to be 84 degrees, so the measure of angle ABD is exactly half of that, or 42 degrees.
Let me know if this helps!