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

[EX Q]: Water is able to diffuse freely between the _ cells.
[EX A]: two

[EX Q]: Flexible shapes are also shapes which have _ obvious way of being attacked.
[EX A]: no

[EX Q]: Phosphates are made of _ phosphorus atom surrounded by four oxygen atoms.
[EX A]:
one