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').

[EX Q]: Many comets have ____ tails.\Question: Choose the right answer from options given a) two b) six c) three d) one
[EX A]: a

[EX Q]: Fluorescent lamps are roughly ____ times more intense than ordinary lightbulbs.\Question: Choose the right answer from options given a) six b) one c) three d) eight
[EX A]: c

[EX Q]: Field lines exist only in ____ dimensions.\Question: Choose the right answer from options given a) two b) ten c) four d) five
[EX A]:
a