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: Most species have four toes, ____ of which are forward-pointing.

SOLUTION: three

PROBLEM: Seasonal records indicate that, in most years, ____ generations occur.

SOLUTION: two

PROBLEM: All addictive drugs have ____ things in common.

SOLUTION:
two