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

Q: Tapirs have hoofed toes, with four toes on the front feet and _ toes on the hind feet.

A: three
****
Q: Puppies can start vaccinations at _ weeks.

A: six
****
Q: Gases inhibit microorganisms by _ mechanisms.

A:
two
****