SELECT (Default is Left) 

Select objects with a single click. By holding down the Control key and clicking the left button, you can select multiple objects. By holding down the Control key and clicking the left button, you can deselect objects that are selected. You can also drag objects by holding down the left button. 

ADJUST (Default is Middle) 

Drag selected objects and keeps the objects selected, or, if an object is not selected, drag that object. You can drop the object on an appropriate target. If a target is not appropriate, the international "no" sign displays while the cursor is over the target. 

MENU 

(Default is Right) 

Display pull-down menus when the cursor is pointing at any title in the menu bar, or display a pop-up menu when the cursor is pointing inside an object on the canvas.