The keyboard option works exactly the same as the Select All option. To use this option, press the [Ctrl] + [A] on your keyboard at the same time. All the objects on your drawing that are visible and can be selected, will highlight in blue.
There are instances when only part of the drawing will be selected:
1. If an object is on a layer that has been ‘Locked’ it cannot be selected.
2. If an object is part of a prototype, it cannot be selected.
If you are using an editing tool that is looking for you to select a specific type of object (i.e., a figure or text), it will only select that specific type of object.