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]: Females become sexually mature at the age of ____ years.
[A]: five


[Q]: Cockroaches have six legs, ____ antennae and some have wings.
[A]: two


[Q]: Ionic mercury can exist in ____ forms.
[A]:
two