Assertion: Noble gases can be liquefied.
Reason: Attractive forces can exist between nonpolar molecules.

Options

A. If both (`A`) and (`R`) are correct and (`R`) is the correct explanation of (`A`).
B. If both (`A`) and (`R`) are correct, but (`R`) is not the correct explanation of (`A`).
C. If (`A`) is correct, but (`R`) is incorrect.
D. If (`A`) is incorrect, but (`R`) is correct.

Explanation

To solve the assertion-reason question, we will analyze both the assertion and the reason step by step.

### Step 1: Analyze the Assertion
**Assertion:** Noble gases can be liquefied.

- Noble gases, such as helium, neon, argon, krypton, xenon, and radon, are known for their very low reactivity due to having a complete valence shell of electrons. However, under certain conditions of low temperature and high pressure, noble gases can indeed be liquefied. This is because, at low temperatures, the kinetic energy of the gas molecules decreases, allowing intermolecular forces to take effect, leading to liquefaction.

### Step 2: Analyze the Reason
**Reason:** Attractive forces can exist between nonpolar molecules.

- Noble gases are nonpolar, and while they do not have permanent dipoles, they can still exhibit weak attractive forces known as London dispersion forces (a type of van der Waals force). These forces arise due to temporary fluctuations in electron density, which create instantaneous dipoles that can induce dipoles in neighboring atoms or molecules. This means that even nonpolar molecules can experience some level of attraction, which is crucial for the liquefaction process.

### Step 3: Determine the Relationship
- The assertion states that noble gases can be liquefied, and the reason explains that attractive forces can exist between nonpolar molecules. Since noble gases are nonpolar and can be liquefied due to these weak attractive forces, the reason provides a valid explanation for the assertion.

### Conclusion
- Both the assertion and reason are correct, and the reason is a correct explanation of the assertion. Therefore, the answer to the question is **A**: Both the assertion and reason are true, and the reason is the correct explanation for the assertion.

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