TASK DEFINITION: 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: Metals often crystallize in a ____ dimensional version of the hexagonal closest packed structure.\Question: Choose the right answer from options given a) one b) seven c) three d) eight

SOLUTION: c

PROBLEM: Youth unemployment is ____ times the adult level.\Question: Choose the right answer from options given a) one b) three c) seven d) no

SOLUTION: b

PROBLEM: Stable nitrogen has ____ protons and seven neutrons.\Question: Choose the right answer from options given a) six b) nine c) seven d) two

SOLUTION:
c