In order to put the senten in formal style, the best revision to make is changing “it’s” to “it is.” So, option B is correct.
Contractions in texts, turn it into an informal style writing.
Formal language is less personal than informal language. It is used when writing for professional or academic purposes like university assignments. Formal language does not use colloquialisms, contractions or first person pronouns such as ‘I’ or ‘We.’ On the other hand, Informal language is more casual and spontaneous.
