Option A - The given sentence is a general statement and not an interrogatory sentence, thus we can't use a question mark here. 'Literature' is a subject and thus 'L' has to be capitalised. Hence, option A is incorrect.
Option B - The given sentence is a general statement and not an exclamatory sentence, thus we can't use an exclamation mark here. 'Literature' is a subject and thus 'L' has to be capitalised. Also, 'poems' are 'John Keat's' possession and so we should use an apostrophe and an 's' here. Hence, option B is incorrect.
Option C - 'Poems' are 'John Keat's' possession and so we should use an apostrophe and an 's' here. Hence, option C is incorrect.
Option D - To show possession of poems, 'John Keat' has been punctuated by an apostrophe and an 's'. 'English Literature' is a subject and hence both the words' first letter have been capitalised. As the sentence is a general statement, it ends with a full stop. Hence, option D is the correct answer.
'Joh Keat's poems are masterpieces in English Literature.'