instruction:
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.
question:
Carbon is able to bond with up to ____ other elements.
answer:
four


question:
Copper has ____ naturally occurring isotopes.
answer:
two


question:
Most children can learn to read when they are ____ years old if properly instructed and motivated.
answer:

four