All modern firearms have three basic groups of parts. what are these parts?

Although firearms have evolved significantly since their inception, the words used to describe their components have remained mostly unchanged. The action, stock, and barrel are the three essential elements of all modern weapons.

Three basic groups of parts are:

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answer; i believe the correct answer is (4) flip a coin as each participant arrives,heads indicates assignment to the first group: tails indicates assignment to the second group;