( Clouds ( ( form ( where ( condensation ( is occurring ) ) ) ) . ) )
(ROOT (S (NP (NNS Clouds)) (VP (VBP form) (SBAR (WHADVP (WRB where)) (S (NP (NN condensation)) (VP (VBZ is) (VP (VBG occurring)))))) (. .)))
Clouds form where condensation is occurring.
(ROOT (S (NP (NNP Condensation)) (VP (MD must) (VP (VB occur) (PP (IN for) (NP (NNS clouds))) (S (VP (TO to) (VP (VB form)))))) (. .)))