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:
Physical abuse occurs in approximately one out of every ____ dating relationships.\Question: Choose the right answer from options given a) six b) four c) one d) ten

Ex Output:
b

Ex Input:
Trees can also be air layered but air layering usually takes four to ____ months to be successful.\Question: Choose the right answer from options given a) five b) nine c) eight d) six

Ex Output:
d