Ctrl Alt ?
On a Chromebook, hold down the Control and the Alt key at the same time. Quickly press once on the question mark key to reveal a screen of keyboard shortcuts for the Chromebook.
Hold down the Control key to see which key combinations work with the Control key. For example, holding down the Control key and quickly pressing L will highlight the URL in the address bar.
Hold down the Alt key to see which key combinations work with the Alt key. For example, holding down Alt and quickly pressing
Hold down Control and the Shift key at the same time to see which key combinations work with these two keys together.