In this task, find the most appropriate number to replace the blank (indicated with _ ) and express it in words.

Q: Infertility affects one in _ couples and affects both men and women.

A: seven
****
Q: Transitional milk is secreted between about four days and _ days postpartum.

A: ten
****
Q: Stars are divided into _ spectral classes according to their color.

A:
seven
****