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

[EX Q]: Black women giving birth have a four to _ higher rate of mortality than white women do.
[EX A]: one

[EX Q]: Dashes are _ times the length of dots.
[EX A]: three

[EX Q]: Natural oxygen is a mixture of _ isotopes.
[EX A]:
three