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]: Pyrimidines contain ____ ring and purines contain two rings.
[EX A]: one

[EX Q]: Nymphs go through ____ instars and a pupa stage before reaching adulthood.
[EX A]: three

[EX Q]: Milk teeth stay in a child up to the age of ____ to eight years.
[EX A]:
seven