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').

Input: Consider Input: Female elephants have babies about ____ years apart, and they have only one each time.\Question: Choose the right answer from options given a) eight b) one c) zero d) three

Output: d


Input: Consider Input: 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

Output: b


Input: Consider Input: Most lakes have ____ layers.\Question: Choose the right answer from options given a) three b) seven c) one d) zero


Output: a