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

[Q]: Disruptive selection can lead to _ new species.
[A]: two


[Q]: Most intestinal worms take _ to four weeks for maturation from their larval stages into adults.
[A]: three


[Q]: Stroke is the number _ killer and the leading cause of disability.
[A]:
three