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').
--------
Question: Females reach sexual maturity around ____ to five year-olds.\Question: Choose the right answer from options given a) four b) five c) one d) ten

Answer: a


Question: Some experts believe whining peaks around the ages of ____ or four.\Question: Choose the right answer from options given a) three b) no c) four d) seven

Answer: a


Question: Adaptation is associated with the reversible methylation of ____ transmembrane receptors.\Question: Choose the right answer from options given a) six b) one c) zero d) four

Answer:
d