Emeralds? 
( Emeralds ? )
(ROOT (NP (NNS Emeralds) (. ?)))
Are they wearing emeralds?
( ( ( Are they ) ( wearing emeralds ) ) ? )
(ROOT (SQ (VBP Are) (NP (PRP they)) (VP (VBG wearing) (NP (NNS emeralds))) (. ?)))