The correct answer is option 'C', the Godavari.

The Wainganga and the Penganga are both tributaries of the Godavari River, which is the fourth longest river in India. Here is an explanation of each river and their relationship to the Godavari:

1. Godavari River:
- The Godavari River is one of the major rivers in India, originating from the Western Ghats in Maharashtra.
- It flows through the states of Maharashtra, Telangana, Andhra Pradesh, and Odisha, before finally emptying into the Bay of Bengal.
- The Godavari River has a total length of about 1,465 kilometers.
- It is often referred to as the "Dakshin Ganga" or the "Ganges of the South" due to its importance and sacredness.

2. Wainganga River:
- The Wainganga River is one of the major tributaries of the Godavari River.
- It originates in the Mahadeo Hills in the state of Madhya Pradesh.
- The river flows through the states of Madhya Pradesh and Maharashtra, before joining the Godavari River in the state of Maharashtra.
- Several other rivers, such as the Wardha and the Pranhita, also join the Godavari River along with the Wainganga, contributing to its overall water flow and volume.

3. Penganga River:
- The Penganga River, also known as the Purna River, is another important tributary of the Godavari River.
- It originates in the Ajanta Hills in Maharashtra.
- The river flows through the states of Maharashtra and Telangana, before joining the Godavari River in the state of Telangana.
- The Penganga River is approximately 724 kilometers long and plays a significant role in the irrigation and agricultural activities of the region.

In conclusion, the Wainganga and the Penganga are tributaries of the Godavari River. These rivers, along with several others, contribute to the overall water flow and drainage system of the Godavari basin, making it one of the most important river systems in India.