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').

Q: Teething begins for most babies around ____ to six months.\Question: Choose the right answer from options given a) three b) four c) five d) seven

A: b
****
Q: Mountain goats have ____ sharp horns.\Question: Choose the right answer from options given a) two b) six c) ten d) four

A: a
****
Q: Neutrons contain one up quark and ____ down quarks.\Question: Choose the right answer from options given a) eight b) three c) no d) two

A:
d
****