You’ve got a whole week to yourself and you can read to your heart’s contents.

The grammatical error of the sentence is in option D. The meaning of a few nouns in plural form is different from their meaning in the singular form. ‘Content’ is such a word. In the given sentence, ‘content’ means “a state of satisfaction”. However, ‘contents’ mean ‘the things that are held or included in something’. Here, the state of being satisfied is mentioned (& ‘heart’ mentioned in the sentence also verifies that.) Thus, it should be ‘heart’s content’ to make the sentence grammatically correct. Correct sentence: You’ve got a whole week to yourself and you can read to your heart’s content.