Which of the following statements concerning unsaturated fats is correct?

Options

A. They have fewer fatty acid molecules per fat molecule
B. They have double bonds in the carbon chains of their fatty acids
C. They generally solidify at room temperature
D. They contain more hydrogen than do saturated fats having the same number of carbon atoms

Explanation

To determine which statement concerning unsaturated fats is correct, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding Unsaturated Fats**:
- Unsaturated fats are fats that contain one or more double or triple bonds in their fatty acid chains. This structural characteristic is key to their properties.

2. **Analyzing Each Option**:
- **Option 1**: "They have fewer fatty acid molecules per fat molecule."
- This statement is incorrect. Unsaturated fats typically have a similar number of fatty acid molecules as saturated fats. The number of fatty acid molecules does not decrease due to unsaturation.

- **Option 2**: "They have double bonds in the carbon chains of their fatty acids."
- This statement is correct. Unsaturated fats are defined by the presence of one or more double bonds in their fatty acid chains.

- **Option 3**: "They generally solidify at room temperature."
- This statement is incorrect. Unsaturated fats are usually liquid at room temperature (e.g., oils), while saturated fats tend to solidify.

- **Option 4**: "Contain more hydrogen than do saturated fats having the same number of carbon atoms."
- This statement is incorrect. Unsaturated fats contain fewer hydrogen atoms than saturated fats because the double bonds reduce the number of hydrogen atoms that can bond to the carbon atoms.

3. **Conclusion**:
- After analyzing all the options, the correct statement concerning unsaturated fats is **Option 2**: "They have double bonds in the carbon chains of their fatty acids."

### Final Answer:
The correct answer is **Option 2**: They have double bonds in the carbon chains of their fatty acids.