He asks Brutus "Et tu<span>, </span>Brute<span>?", which translates to something along the lines of "You too, Brutus?". Caesar is expressing his surprise at his friend being in league with the conspirators that were stabbing him.</span>
Marissa trashed the doughnuts because they were totally gross: very informal.
Marissa threw the doughnuts in the trash can because she knew they had exceeded their expiration date: informal.
Marissa understood the hazards of eating expired doughnuts, and with very little hesitation she deposited the aforementioned eatables into the garbage receptacle: formal.