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: Babies start swimming lessons as young as ____ weeks old.

A: four
****
Q: Pertussis is highly contagious with symptoms that can linger ____ to ten weeks.

A: six
****
Q: Retraction requires the contraction of ____ internal muscles .

A:
two
****