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').

Elephants have four molars, which are replaced ____ times, for a total of six sets in a lifetime.\Question: Choose the right answer from options given a) five b) no c) three d) one
a

Huntsman spiders have large, hairy bodies with ____ long legs.\Question: Choose the right answer from options given a) three b) eight c) ten d) six
b

Robot arms are of ____ types.\Question: Choose the right answer from options given a) eight b) ten c) zero d) two

d