TASK DEFINITION: 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').
PROBLEM: Natural indium contains ____ isotopes.\Question: Choose the right answer from options given a) one b) eight c) two d) seven

SOLUTION: c

PROBLEM: Songbirds have ____ sets of vocal chords.\Question: Choose the right answer from options given a) six b) two c) eight d) ten

SOLUTION: b

PROBLEM: Most spiders live only a year or so, molting five or ____ times before reaching maturity.\Question: Choose the right answer from options given a) three b) six c) four d) ten

SOLUTION:
b