Using a windows computer, to expand a branch of the folder tree you would

A folder can include everything from documents and music, to applications [like Word or Excel or your favorite browser]. But computer folders can also contain other folders, lots of them, and those sub-folders can contain folders of their own. This is the called folder tree. The trunk of the tree is the Desktop. Then there are several folders like Recycle Bin, Control Panel,..The most important branch is the one called ‘Libraries’. Here are the Photos, Music, Videos,...
Using a windows computer, to expand a branch of the folder tree you would right click beside various folders and drives to expand the folder tree.

4because of my mind tells me to pick 4