Final answer:
The running back's total yardage is B) -3 yards.
Step-by-step explanation:
The running back gained 9 yards in the first half and lost 12 yards in the second half, which means he moved in the opposite direction.
To find the running back's total yardage, we can add the positive yardage gained in the first half (+9 yards) and the negative yardage lost in the second half (-12 yards).
So, 9 yards (first half) + (-12 yards) (second half) = -3 yards
Therefore, the running back's total yardage is -3 yards.
This means that the running back ended the game with a net loss of 3 yards.
So the correct answer is B) -3 yards.