Q: Given a sentence with a missing word, pick the answer option that best fills out the missing word in the sentence. Indicate each answer with its index ('a', 'b', 'c', 'd').
Japanese archaeologists recognize, in general terms, four prehistoric and ____ historic periods.\Question: Choose the right answer from options given a) seven b) ten c) four d) eight
A:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
c