'Moribund Delta' is a subdivision of which of the following delta?

1. A

   Krishna-Godavari Delta

   The Krishna–Godavari delta is an active/growing east-coast delta. ‘Moribund delta’ is not its standard subdivision name in this question.

2. B

   Mahanadi Delta

   The Mahanadi delta (Odisha) is not the textbook ‘moribund delta’ of Bengal school geography.

3. C

   Bengal Delta

   Bagh’s/ Bagchi’s Bengal delta is classically divided into moribund, mature and active parts. The moribund delta is the dead/dying western old Ganga–Bhagirathi spill area of the Bengal delta (Nadia–Murshidabad type tracts). That is why (c) is the official key.

4. D

   Cauvery Delta

   The Cauvery delta is a separate, still-evolving Tamil Nadu delta, not this subdivision.

Summary. Official key is (c). ‘Moribund delta’ is a subdivision of the Bengal (Ganga–Brahmaputra) delta — the decaying western old delta — not Krishna–Godavari, Mahanadi or Cauvery.