Solution:An adverb of frequency is a word that can be placed after the noun or pronoun in a sentence to give more information about the verb, adjective or another adverb.Some examples of adverbs of frequencies are
- rarely,
- often,
- always,
- never
- and sometimes.
Similarly, 'often' as an adverb of frequency is perfectly used in option 'c'.
Hence, 'Radha often goes to Nagpur' is the most appropriate answer.