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

[EX Q]: Polymorphism occurs in all species and the mandibles bear _ teeth.
[EX A]: four

[EX Q]: Prokaryotes mean they have _ nucleus in which they store genetic material.
[EX A]: no

[EX Q]: Excess potassium induces larval metamorphosis in _ marine invertebrate species.
[EX A]:
four