( ( ( A ( water molecules ) ) ( -LRB- ( ( H ( 2 O ) ) -RRB- ) ) ) ( ( is ( made ( of ( ( ( ( ( 2 ( hydrogen atoms ) ) ( -LRB- ( H -RRB- ) ) ) and ) ( one ( oxygen atom ) ) ) ( -LRB- ( O -RRB- ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT A) (NN water) (NNS molecules)) (PRN (-LRB- -LRB-) (NP (NNP H) (QP (CD 2) (CD O))) (-RRB- -RRB-))) (VP (VBZ is) (VP (VBN made) (PP (IN of) (NP (NP (CD 2) (NN hydrogen) (NNS atoms)) (PRN (-LRB- -LRB-) (NP (NNP H)) (-RRB- -RRB-)) (CC and) (NP (CD one) (NN oxygen) (NN atom)) (PRN (-LRB- -LRB-) (NP (NNP O)) (-RRB- -RRB-)))))) (. .)))
A water molecules (H 2 O) is made of 2 hydrogen atoms (H) and one oxygen atom (O).
(ROOT (S (NP (NP (CD 2) (NN hydrogen)) (, ,) (NP (CD 1) (NN oxygen) (NNS atoms))) (VP (VBP combine) (S (VP (TO to) (VP (VB make) (PRT (RP up)) (NP (NP (DT a) (NN molecule)) (PP (IN of) (NP (NN water)))))))) (. .)))
2 hydrogen, 1 oxygen atoms combine to make up a molecule of water.