The correct option is A a
Options A and B: 'A' and 'an' both refer to non-specific nouns.
The only difference is that 'a' is used for nouns that begin with a consonant: a man, a bat, a child; 'm', 'b', 'c' are consonants.
'An' is used for nouns that begin with a vowel: an animal, an eagle, an ice cream; 'a', 'e' 'i' are vowels
When an adjective modifies the noun, then we use 'a' and 'an' according to the initial of the adjective, and not the noun.
Here, 'social' is the adjective; it begins with a consonant 's'. So, we use 'a'.
Hence option A is correct and B is incorrect.
Option C: 'The' is a definite article that modifies specific nouns, whose identity is made known: the man on the street.
'Animal' is a general word that refers to a kind of living being, and does not refer to a specific animal.
Hence option C is incorrect.
Option D is incorrect because the noun uses an article, 'a'.