Cell membranes are mainly composed of `:`

Options

A. carbohydrates
B. proteins
C. phospholipids
D. fats

Explanation

**Step-by-Step Solution:**

1. **Understanding Cell Membranes**: Cell membranes, also known as plasma membranes, are crucial structures that surround cells. They serve as barriers that separate the internal environment of the cell from the external environment.

2. **Components of Cell Membranes**: The main components of cell membranes include proteins, lipids, and carbohydrates. Each of these components plays a vital role in the function and structure of the membrane.

3. **Focus on Lipids**: Among the lipids, phospholipids are the most abundant type found in cell membranes. They are essential for forming the structure of the membrane.

4. **Phospholipid Structure**: Phospholipids consist of a hydrophilic (water-attracting) "head" and two hydrophobic (water-repelling) "tails." This unique structure allows phospholipids to arrange themselves into a bilayer, with the hydrophilic heads facing outward towards the water inside and outside the cell, while the hydrophobic tails face inward, away from the water.

5. **Conclusion**: Given that phospholipids are the most abundant type of lipids in cell membranes and are critical for the formation of the phospholipid bilayer, we can conclude that cell membranes are mainly composed of phospholipids.

**Final Answer**: Cell membranes are mainly composed of **phospholipids**.

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