Click Tools > Options to see the selection options.
Select with Right-button menus
Choose to enable a pop-up menu substitute for the Combine Selections dialog box. When selecting entities, a right-click to end selection displays the pop-up Selection Menu. We think that this method is more efficient.
Enable Left-button Preselecting
Choose this option if you wish to select entities first, and then select an editing command. This method conforms to the common Windows methodology. CC3 has always asked you for the editing command first, and then for the applied entities. Leave this option unchecked to preserve the traditional operation-selection method. We recommend that you do not check this option.