Assertion : Phospholipids form bimolecular layer in
aqueous medium .
Reason : phospholipid molecules are amphipathic .

Options

A. If both assertion & Reason are ture & the Reason is a correct explanation of the Assertion
B. If both Assertion & Reason ar True but Reason is not a correct explantation of the Assertion
C. If Assertion is True but the Reason is False
D. If both Assertion & Reason are false

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion**: The assertion states that phospholipids form a bimolecular layer in aqueous medium. This is a fundamental characteristic of phospholipids, which are essential components of cell membranes.

2. **Understanding the Reason**: The reason provided is that phospholipid molecules are amphipathic. Amphipathic molecules have both hydrophilic (water-loving) and hydrophobic (water-hating) parts. This property is crucial for the formation of the bimolecular layer.

3. **Explaining the Structure of Phospholipids**: Phospholipids consist of a hydrophilic polar head and two hydrophobic non-polar tails. In an aqueous environment, the hydrophilic heads face outward towards the water, while the hydrophobic tails face inward, away from the water. This arrangement leads to the formation of a bimolecular layer.

4. **Conclusion**: Since both the assertion and the reason are true, and the reason correctly explains why the assertion is true, we can conclude that the correct answer is that both the assertion and reason are true, and the reason is the correct expression of the assertion.

### Final Answer:
The correct answer is A: Both assertion and reason are true, and reason is the correct expression of assertion.