National Highways are an important part of a country's transportation network as they connect major cities, ports, and industrial centers. In India, the responsibility for the development and maintenance of National Highways lies with the National Highways Authority of India (NHAI).

Among the given options, Maharashtra has the highest number of National Highways. Here is a detailed explanation:

1. Madhya Pradesh:
- Madhya Pradesh is the second-largest state in India in terms of area.
- It has a total of 20 National Highways passing through it.
- These National Highways connect important cities and towns within the state, as well as provide connectivity to neighboring states.

2. Punjab:
- Punjab is a state located in the northern part of India.
- It has a total of 19 National Highways passing through it.
- These National Highways connect Punjab to various parts of the country, including neighboring states and major cities.

3. Maharashtra:
- Maharashtra is the third-largest state in India in terms of area and the second-most populous state.
- It has the highest number of National Highways among the given options, with a total of 50 National Highways passing through it.
- Maharashtra is a major industrial and commercial hub, and these National Highways play a crucial role in connecting important cities, ports, and industrial areas within the state.

4. Tripura:
- Tripura is a small state located in northeastern India.
- It has a total of 4 National Highways passing through it.
- These National Highways connect Tripura to neighboring states and provide important connectivity within the state.

In conclusion, Maharashtra has the highest number of National Highways among the given options. The presence of 50 National Highways in Maharashtra is due to its large size, population, and economic significance. These National Highways play a vital role in facilitating transportation and connectivity within the state, as well as connecting Maharashtra to other parts of the country.

Correct option is C . Maharashtra