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: Water weighs about ____ pounds per gallon.\Question: Choose the right answer from options given a) seven b) ten c) zero d) nine

SOLUTION: b

PROBLEM: Firebrat eggs hatch in about ____ weeks.\Question: Choose the right answer from options given a) ten b) one c) two d) no

SOLUTION: c

PROBLEM: Some sources claim there are more like ____ million vertebrate animals in zoos.\Question: Choose the right answer from options given a) six b) five c) one d) three

SOLUTION:
b