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

Q: Sturgeons are shark-like in form but are unique in having _ rows of bony plates along the body.

A: five
****
Q: Hoatzin has typical foot with _ toes forwards and one backwards.

A: three
****
Q: Yellow fever begins suddenly after an incubation period of _ to five days.

A:
three
****