## **Core Concept**
The question tests knowledge of vaccines contraindicated in pregnancy, focusing on live attenuated vaccines and their potential risks to the fetus.

## **Why the Correct Answer is Right**
The correct answer, **B. Varicella vaccine**, is a live attenuated vaccine. Live vaccines are generally contraindicated in pregnancy due to the theoretical risk of transmission of the vaccine virus to the fetus, although such occurrences are rare. The Varicella vaccine is made from a live, attenuated virus and is thus avoided in pregnant women.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is not provided, but typically, inactivated or killed vaccines are safe in pregnancy.
- **Option C:** This option is not provided, but similar to option A, if it were an inactivated vaccine, it would not be contraindicated.
- **Option D:** This option is not provided, but if it represented a vaccine not specifically known to be live or particularly risky in pregnancy, it would be incorrect for being less directly related to the concern of live vaccines.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that **live vaccines** (like Varicella, MMR, and BCG) are generally avoided in pregnancy due to the theoretical risk of fetal infection, whereas **inactivated vaccines** (like Hepatitis A and B, and Tdap) are considered safe and sometimes recommended during pregnancy to protect against specific diseases.

## **Correct Answer:** B. Varicella vaccine.