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

[EX Q]: Humans host _ species of louse, the head louse , the body louse and the pubic louse .
[EX A]: three

[EX Q]: Some women experience a labor of three to _ days.
[EX A]: five

[EX Q]: Most infected people have _ symptoms and are never diagnosed.
[EX A]:
no