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.

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


[Q]: Mollusks have one or ____ hearts.
[A]: two


[Q]: Banks play ____ important roles in the money market.
[A]:
three