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: Ammonia is among the ____ most abundantly produced chemicals in the world.\Question: Choose the right answer from options given a) five b) zero c) no d) eight

SOLUTION: a

PROBLEM: Calves can swim ____ days after they are born.\Question: Choose the right answer from options given a) ten b) two c) zero d) one

SOLUTION: b

PROBLEM: Terrorism is a problem which has troubled the international community for more than ____ decades.\Question: Choose the right answer from options given a) zero b) three c) nine d) four

SOLUTION:
b