To determine which of the given pairs is/are correctly matched, let`s examine each pair individually:

1. Chambal - Narmada: The Chambal River is a tributary of the Yamuna River, not the Narmada River. The Chambal River originates in the Vindhya Range in Madhya Pradesh, India, and joins the Yamuna River in Uttar Pradesh. The Narmada River, on the other hand, is a major river in central India that flows through the states of Madhya Pradesh, Maharashtra, and Gujarat. Therefore, this pair is not correctly matched.

2. Sone - Yamuna: The Sone River is a tributary of the Ganges River, not the Yamuna River. It originates in the state of Chhattisgarh, India, and flows through Madhya Pradesh and Bihar before joining the Ganges River in Uttar Pradesh. The Yamuna River is a major tributary of the Ganges and passes through the states of Uttarakhand, Himachal Pradesh, Haryana, Delhi, and Uttar Pradesh. Hence, this pair is not correctly matched.

3. Manas - Brahmaputra: The Manas River is indeed a tributary of the Brahmaputra River. It originates in Bhutan and flows through the Indian state of Assam, where it merges with the Brahmaputra. The Brahmaputra River is one of the major rivers of Asia, flowing through Tibet, India, and Bangladesh. Therefore, this pair is correctly matched.

Based on the analysis above, we can conclude that the only correctly matched pair is "3. Manas - Brahmaputra." Therefore, the correct option is "Option 4: 3 only."