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.

[EX Q]: Some animals have only ____ or three chambers .
[EX A]: two

[EX Q]: Aardvarks have ____ toes on the front feet and five toes on their back feet.
[EX A]: four

[EX Q]: Aquifers occur in ____ types of geologic formations.
[EX A]:
two