Which one of the following is not an antibiotic?
Ofloxacin
Penicillin
Oxytocin
Ampicillin
Oxytocin is not an antibiotic but is a hormone that's produced in the hypothalamus and released into the bloodstream by the pituitary gland. Its main function is to facilitate childbirth, which is one of the reasons it is called the "love drug" or "love hormone."
Therefore, 3rd option is correct.