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: Many tortoises can retract their head, their ____ limbs and tail into the shell for protection.\Question: Choose the right answer from options given a) no b) one c) two d) four

SOLUTION: d

PROBLEM: Redwoods reproduce ____ ways.\Question: Choose the right answer from options given a) zero b) two c) six d) nine

SOLUTION: b

PROBLEM: Blood flows in one direction through the ____ chambers with the aid of the four heart valves.\Question: Choose the right answer from options given a) four b) three c) two d) no

SOLUTION:
a