Introduction:
Pepo fruit is a specific type of fruit that belongs to the family Cucurbitaceae. In this response, we will discuss the reasons why option 'C' (Cucurbitaceae) is the correct answer for the relationship of Pepo fruit.

Explanation:
Cucurbitaceae Family:
- The Cucurbitaceae family is a plant family that consists of various flowering plants. It is commonly known as the gourd family.
- This family includes many well-known fruits and vegetables such as watermelon, cucumber, pumpkin, zucchini, and squash.
- The fruits belonging to this family are typically large and fleshy with a hard outer rind or shell.
- The fruits usually have a hollow center filled with seeds.

Pepo Fruit:
- Pepo fruit is a specific type of fruit that falls under the Cucurbitaceae family.
- It is a fleshy fruit with a hard outer rind or exocarp.
- Examples of pepo fruits include watermelon, cucumber, pumpkin, and squash.
- The fruit is typically large and contains numerous seeds embedded in the flesh.
- Pepo fruits have a characteristic fleshy pulp and a well-developed endocarp.

Other Options:
Now, let's discuss the other options and why they are not the correct answer for the relationship of Pepo fruit.

a) Leguminosae:
- Leguminosae, also known as the Fabaceae family, is the family of legumes or pea plants.
- Legume fruits are pod-like structures that split open along two sides.
- Examples of legume fruits include peas, beans, lentils, and peanuts.
- Pepo fruits do not belong to the Leguminosae family, as they have a different fruit structure.

b) Cruciferae:
- Cruciferae, also known as Brassicaceae, is the family of cruciferous vegetables.
- Cruciferous vegetables are characterized by their four-petal flowers and cross-shaped arrangement of petals.
- Examples of cruciferous vegetables include broccoli, cauliflower, cabbage, and kale.
- Pepo fruits do not belong to the Cruciferae family, as they have a different fruit structure.

d) Liliaceae:
- Liliaceae is the family of lilies and other similar flowering plants.
- Liliaceae family includes plants with bulbous, cormous, or rhizomatous roots.
- Examples of Liliaceae family plants include lilies, tulips, onions, and garlic.
- Pepo fruits do not belong to the Liliaceae family, as they have a different fruit structure.

Conclusion:
In conclusion, Pepo fruit is related to the Cucurbitaceae family. This family consists of various fruits and vegetables, including watermelon, cucumber, pumpkin, and squash. The Pepo fruit is characterized by its fleshy pulp, hard outer rind, and numerous seeds embedded in the flesh. The other options mentioned in the question, Leguminosae, Cruciferae, and Liliaceae, do not have the same fruit structure as the Pepo fruit.