The rivers Godavari, Mahanadi, Narmada and Tapi are among the largest rivers in India. The lengths of these rivers vary and this is what the question asks to arrange in descending order.

Option 2 is the correct answer. Here is why other options are incorrect:

Option 1: Godavari—Mahanadi—Narmada—Tapi. This is incorrect as Narmada is longer than Mahanadi.

Option 3: Narmada—Godavari—Tapi—Mahanadi. This is incorrect as Godavari is longer than Narmada.

Option 4: Narmada—Tapi—Godavari—Mahanadi. This is incorrect as Godavari is longer than both Narmada and Tapi.

To correctly answer this question, one must know the approximate lengths of these rivers. Godavari is the longest among the four (approximately 1465 kilometers), followed by Narmada (approximately 1312 kilometers), Mahanadi (approximately 851 kilometers), and lastly the Tapi (approximately 724 kilometers). Hence, in descending order of their lengths, the sequence is: Godavari—Narmada—Mahanadi—Tapi.