believable that you feel what they feel 
(ROOT (ADJP (JJ believable) (SBAR (IN that) (S (NP (PRP you)) (VP (VBP feel) (SBAR (WHNP (WP what)) (S (NP (PRP they)) (VP (VBP feel)))))))))
(ROOT (ADJP (JJ ) (SBAR (IN ) (S (NP (PRP )) (VP (VBP ) (SBAR (WHNP (WP )) (S (NP (PRP )) (VP (VBP )))))))))