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

[EX Q]: Mice are fertile animals because female mice come into heat every _ to five days.
[EX A]: four

[EX Q]: Covalent bonds arise when _ atoms share electrons .
[EX A]: two

[EX Q]: Quarks There are _ quarks that combine to make sub-atomic particles.
[EX A]:
six