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').

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
c

Copper is ____ times higher in dog liver than in human liver.\Question: Choose the right answer from options given a) three b) ten c) six d) one
b

Some manatees have three or ____ nails on the tip of each flipper.\Question: Choose the right answer from options given a) eight b) ten c) four d) one

c