How To Show Menu Items of Armature in Blender

This is a trouble shooting in Blender.

Problem

The items “Single Bone”, “Human”, “Animal” and so on doesn’t show even though Add > Armature clicked. And the menu items about Armature doesn’t exist.

Environment

Blender2.83(LTS)
Windows10

Solution

Activate “Rigging: Rigify” addon.

Click File > Preferences and search and activate the addon named “Rigging: Rigify”.