CMenu colorMenu; colorMenu.LoadMenu(ID_MY_COLOR_MENU); CMenu* pSubMenu = colorMenu.GetSubMenu(0); pSubMenu->CheckMenuRadioItem(ID_MY_RED_ITEM, ID_MY_BLUE_ITEM, ID_MY_RED_ITEM, MF_BYCOMMAND);This code loads the menu from the resource ID `ID_MY_COLOR_MENU`, gets a pointer to the first submenu, and then calls `CheckMenuRadioItem()` with the command IDs of the "Red" and "Blue" items, and the ID of the item to check, which is "Red". The package library for this function is the Microsoft Foundation Class (MFC) library in C++.