Which of the following is a tocolytic medication?

Tocolytic medications are used to suppress premature labor by inhibiting uterine contractions. Among the choices provided, terbutaline is a medication specifically classified as a tocolytic. It is a beta-agonist that relaxes the smooth muscles of the uterus, effectively delaying preterm childbirth. This action helps to give time for further fetal development or for potential transfer to a facility equipped for neonatal care.

In contrast, aspirin is primarily used as an anti-inflammatory and antipyretic agent, while ibuprofen is a non-steroidal anti-inflammatory drug (NSAID) used for pain relief and to reduce inflammation. Penicillin is an antibiotic used to treat bacterial infections. None of these options have the tocolytic properties that terbutaline does, making terbutaline the correct choice.