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: Food chains consist of ____ trophic levels.\Question: Choose the right answer from options given a) ten b) three c) one d) four

SOLUTION: d

PROBLEM: Litters contain from one to ____ kittens, and tend to be much larger when prey is abundant.\Question: Choose the right answer from options given a) three b) four c) two d) seven

SOLUTION: b

PROBLEM: River dolphins are ____ living species of dolphin, which reside in freshwater rivers and estuaries.\Question: Choose the right answer from options given a) seven b) four c) no d) eight

SOLUTION:
b