The correct option is C the
In the given sentence, we are referring to the shops located in a specific place, the city center. Hence the noun 'shops' is specific for which we use the definite article 'the', option C is the correct option. Options A and B are incorrect because they're both indefinite articles which are used for nouns which are non-specific and singular, whereas 'shops' is specific and plural. Option D is incorrect because in the sentence, 'most' has been used for shops which were closed. If 'most' of the shops were closed, only a few must be open, and not 'many' because it contradicts the statement, by suggesting that a large number of shops were open, when in fact a large number were closed.