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: Most children start primary school at ____ years of age.

A: five
****
Q: Human gestation is divided into three trimesters of ____ months each.

A: three
****
Q: Stem cells form within ____ days of conception.

A:
four
****