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

[Q]: Morocco has _ perennial rivers and many dams have been built with potential for power generation.
[A]: four


[Q]: Porcine insulin has _ different amino acid and bovine insulin has three different amino acids.
[A]: one


[Q]: Earthworms have _ means of regulating temperature or water loss.
[A]:
no