The noble gas which behaves abnormally in liquid state is 

Options

A. Xe
B. Ne
C. He
D. Ar

Answer

To solve the question regarding which noble gas behaves abnormally in the liquid state, we will follow these steps:

### Step-by-Step Solution:

1. **Identify the Noble Gases**: The noble gases include helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). However, for this question, we are only considering helium, neon, argon, and xenon.

2. **Understand the Behavior of Helium**: Helium is unique among the noble gases. It remains a liquid even at very low temperatures. When cooled below 4.18 K, helium transitions from a gaseous state to a liquid state known as helium I.

3. **Cooling Helium Further**: When helium is cooled further to about 2.2 K, it becomes helium II. This state is characterized by its unusual properties, such as being a superfluid, which allows it to flow without viscosity.

4. **Define Superfluidity**: Superfluidity is a phase of matter that behaves like a fluid with zero viscosity. This means that it can flow without losing energy, which is an abnormal behavior compared to typical liquids.

5. **Conclusion**: Based on the unique properties of helium in its liquid state, particularly at low temperatures, we conclude that the noble gas which behaves abnormally in the liquid state is **helium**.

### Final Answer:
The noble gas which behaves abnormally in liquid state is **helium**.

---