These alone could have valuable uses.
( These ( alone ( ( could ( have ( valuable uses ) ) ) . ) ) )
(ROOT (S (NP (DT These)) (ADVP (RB alone)) (VP (MD could) (VP (VB have) (NP (JJ valuable) (NNS uses)))) (. .)))
They may be valuable. 
( They ( ( may ( be valuable ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (MD may) (VP (VB be) (ADJP (JJ valuable)))) (. .)))