The answer should be D because the word "was" almost always makes the sentence past tense. (Im sorry if this is not correct but it should be, Im not the smartest cup of tea)
D. Possessive.
Howard's apostrophe means that it is his, therefore possesive.
Answer:
O Robert F. Foster: Modern Ireland 1600-1972. Dublin, 2011 is the correct citation
Explanation: