Text edit is the only one of the three you can use arrows with. In safari and mail, you must use vo commands. The way to get round this with email is to forward, reply or copy the message into text edit. The way to get round it with safari is to copy the page into text edit and convert it to plain text which you may also have to do with the message depending on format.
I don't know off hand how to copy sentences with a keystroke.
