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: Fossil fuels come in ____ major forms coal, oil and natural gas.

SOLUTION: three

PROBLEM: Deer show ____ symptoms of the disease.

SOLUTION: no

PROBLEM: Natural silicon contains ____ isotopes.

SOLUTION:
three