This is Susan.
( This ( ( is Susan ) . ) )
(ROOT (S (NP (DT This)) (VP (VBZ is) (NP (NNP Susan))) (. .)))
This is Bob. 
( This ( ( is Bob ) . ) )
(ROOT (S (NP (DT This)) (VP (VBZ is) (NP (NNP Bob))) (. .)))