Why does the function of the hormone oxytocin in the progression of labor.....

Why does the function of the hormone oxytocin in the progression of labor during childbirth illustrate a positive feedback mechanism?
A. Because an increase in oxytocin level decreases the contractions
B. Because an increase in oxytocin level increases the contractions
C. Because an increase in oxytocin level has no effect on the contractions

b