TASK DEFINITION: Given a sentence, fill out the missing word with a 'no' or a number (between zero and ten). You should write the numbers with english alphabet, like: four instead of 4.
PROBLEM: Rattlesnakes breed only every ____ to three years.

SOLUTION: two

PROBLEM: Green lines represent the boundaries between the ____ hemispheres.

SOLUTION: two

PROBLEM: Mayflies emerge as adults, mate, and lay their eggs in the space of about ____ days.

SOLUTION:
three