Have you read the documentation or checked with the manufacture of the VNC Client you're using!?
It is not unusual to have to use a different hotkey combo when one wants it sent to a remote Desktop. As an example the hotkey combo Ctrl+Alt+Del is typically Ctrl+Alt+Insert or Ctrl+Alt+End, depends on the client. Sometimes one must use the Fn key in combo with other keys, like on some Notebooks. Some VMC clients have a menu command for common hotkey combos.
Bottom line is read the documentation for the VNC client you're using and if it's not there then go to the VNC Client Manufactures web site and look for the answers there or Google it! 
Balubeto Balubeto wrote: I use UltraVNC Viewer 1.1.8.0. Could you tell me how I should do to send the sequences mentioned above to a Windows VM?
NO! I'm not going to tell you because I asked you, "Have you read the documentation or checked with the manufacture of the VNC Client you're using!?" and of course I already knew the answer because if you had you'd not need to ask the question if the first place! So either you can't take a hint or your just plain lazy!
Try RTFM instead of asking questions that are answered by the documentation! 