you feel alive - which is what they did 
(ROOT (S (S (NP (PRP you)) (VP (VBP feel) (ADJP (JJ alive)))) (, -) (SBAR (WHNP (WDT which)) (S (VP (VBZ is) (SBAR (WHNP (WP what)) (S (NP (PRP they)) (VP (VBD did)))))))))
(ROOT (S (S (NP (PRP )) (VP (VBP ) (ADJP (JJ )))) (, ) (SBAR (WHNP (WDT )) (S (VP (VBZ ) (SBAR (WHNP (WP )) (S (NP (PRP )) (VP (VBD )))))))))