## Core Concept
The question pertains to the safety of drugs during pregnancy, which is a critical consideration in pharmacology and obstetrics. The safety of a drug during pregnancy is often categorized based on its potential to cause harm to the fetus. The **FDA pregnancy categories**, although recently updated to a narrative system, historically helped in classifying drugs based on their risk.

## Why the Correct Answer is Right
The correct answer, **Penicillin G**, is considered relatively safe during pregnancy. Penicillin G is an antibiotic that belongs to the beta-lactam class. It works by inhibiting cell wall synthesis in bacteria, which makes it effective against a wide range of bacterial infections. Its use during pregnancy is generally considered safe for both the mother and the fetus when used appropriately.

## Why Each Wrong Option is Incorrect
- **Option A:** Without the specific drug listed, we cannot directly assess its safety. However, many drugs are contraindicated in pregnancy due to their teratogenic effects or potential to cause harm to the fetus.
- **Option B:** Similarly, without specifics, it's hard to evaluate, but certain drugs like **tetracyclines** (e.g., doxycycline) are contraindicated in pregnancy due to the risk of inhibiting bone growth and causing tooth discoloration in the fetus.
- **Option D:** Again, lacking specifics, if we consider drugs like **Warfarin**, it's known to have teratogenic effects and is usually avoided in pregnancy, especially during the first trimester.

## Clinical Pearl / High-Yield Fact
A key point to remember is that **penicillin** and other **beta-lactam antibiotics** are often considered safe during pregnancy, making them useful for treating infections that occur during this period. However, always consider the specific condition being treated and the gestational age of the fetus.

## Correct Answer Line
**Correct Answer: C. Penicillin G.**