The correct answer is:

1. Bandarpunch - Yamuna

2. Bara Shigri - Chenab

4. Siachen - Nubra

Therefore, the correct option is a. 1, 2 and 4.

Explanation:

Glaciers are a major source of fresh water in the world and they feed several important rivers. The rivers mentioned in the pairs are:

1. Yamuna - It originates from the Yamunotri glacier and is fed by several smaller rivers and streams, including the Bandarpunch glacier.

2. Chenab - It is formed by the confluence of two rivers, Chandra and Bhaga, near Tandi in Himachal Pradesh. The Bara Shigri glacier is one of the largest glaciers in the Himalayas and feeds the Chandra river.

3. Mandakini - It is a tributary of the Alaknanda river and originates from the Chorabari glacier in Uttarakhand.

4. Nubra - It is a tributary of the Shyok river in Ladakh and originates from the Siachen glacier, which is the world`s second-longest glacier outside the polar regions.

5. Manas - It is a transboundary river that flows through Bhutan, India, and Bangladesh. The Zemu glacier is located in the eastern Himalayas and feeds the Tista river, which is a tributary of the Brahmaputra.

Hence, option a. 1, 2 and 4 are the correctly matched pairs.