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').

Potential energy is divided into ____ different types of energy.\Question: Choose the right answer from options given a) eight b) three c) zero d) two
b

Water weighs about ____ pounds per gallon.\Question: Choose the right answer from options given a) seven b) ten c) zero d) nine
b

Masturbation can get really old after six or ____ years.\Question: Choose the right answer from options given a) no b) seven c) zero d) five

b