Detailed Instructions: 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').
Problem:Blood has ____ main functions.\Question: Choose the right answer from options given a) three b) seven c) nine d) six
Solution:

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
a