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').

Ex Input:
Water is the only natural substance which exists in all ____ states of matter in nature.\Question: Choose the right answer from options given a) no b) eight c) six d) three

Ex Output:
d


Ex Input:
Sexual maturity occurs at three to four years for females and ____ to five years for males.\Question: Choose the right answer from options given a) nine b) seven c) five d) four

Ex Output:
d


Ex Input:
Heat has ____ mass .\Question: Choose the right answer from options given a) no b) ten c) five d) four

Ex Output:

a