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

[EX Q]: Compound machines are _ or more simple machines working together.
[EX A]: two

[EX Q]: Scientists use a characteristic to classify animals into _ groups.
[EX A]: two

[EX Q]: Carbon forms _ well-known allotropes, graphite and diamond.
[EX A]:
two