Mahanadi River does not make an estuary. An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environments.

Introduction:
In this question, we are asked to identify the river that does not make an estuary out of the given options. An estuary is a partly enclosed coastal body of brackish water with one or more rivers or streams flowing into it. Let's analyze each option to determine the correct answer.

Analysis:
a) Narmada:
The Narmada river is a west-central Indian river that flows through the states of Madhya Pradesh, Maharashtra, and Gujarat. It forms an estuary where it meets the Arabian Sea. Therefore, option a) is not the correct answer.

b) Tapi:
The Tapi river is a river in central India that flows through the states of Maharashtra and Gujarat. It also forms an estuary where it meets the Arabian Sea. Therefore, option b) is not the correct answer.

c) Mandovi:
The Mandovi river is a river in western India that flows through the state of Goa. It forms an estuary where it meets the Arabian Sea. Therefore, option c) is not the correct answer.

d) Mahanadi:
The Mahanadi river is a major river in East Central India that flows through the states of Chhattisgarh and Odisha. It does not form an estuary but rather a delta where it meets the Bay of Bengal. Therefore, option d) is the correct answer.

Conclusion:
Out of the given options, the river that does not make an estuary is the Mahanadi river (option d). It forms a delta instead of an estuary where it meets the Bay of Bengal.

Mahanadi,

Narmada flows from Rift valley and doesn't form estuary,
Mandvi is short distance river and from less height.