The nurse is caring for a client who is 21-weeks pregnant and requires the administration of various medications. The nurse understands that different medications are classified on their potential interaction with the mother's fetus. From the list of options below, match the correct medication category to its corresponding description.

A.    Category A:
Medications classified as Category A are considered the safest during pregnancy. They have been well-studied in pregnant humans, and no risk to the fetus has been demonstrated. This classification means that adequate and well-controlled studies have shown no evidence of harm to the fetus in the first trimester and no risk in later trimesters.

B.    Category C:
Category C medications have shown potential risks to the fetus in animal studies, and there are no well-controlled studies in humans. The benefits of the medication may outweigh the potential risks, but caution is advised. These medications are used when the potential benefits justify the potential risks to the fetus.

C.    Category X:
Category X medications are contraindicated in pregnancy due to evidence of fetal abnormalities or risks that outweigh any potential benefits. These medications have demonstrated clear evidence of harm to the fetus in both human and animal studies, and their use is not recommended during pregnancy.

D.    Category B:
Category B medications have shown no risk to animal fetuses, but there is a lack of adequate and well-controlled studies in pregnant humans. The absence of evidence of harm in animal studies suggests that these drugs are generally considered safe, though their effects on human fetuses are not well-documented.