( ( ( The ( two substances ) ) ( that attract ) ) ( ( must ( be magnetic ) ) . ) )
(ROOT (S (NP (NP (DT The) (CD two) (NNS substances)) (SBAR (WHNP (WDT that)) (S (VP (VBP attract))))) (VP (MD must) (VP (VB be) (NP (JJ magnetic)))) (. .)))
The two substances that attract must be magnetic.
(ROOT (S (S (VP (VBG Increasing) (NP (NP (DT the) (NN distance)) (PP (IN between) (NP (DT the) (CD two) (NNS magnets)))))) (VP (MD will) (VP (VB cause) (NP (DT a) (NN decrease)) (PP (IN in) (NP (NP (DT the) (NN force)) (PP (IN of) (NP (NP (NN attraction)) (PP (IN between) (NP (CD two) (NNS magnets))))))))) (. .)))
Increasing the distance between the two magnets will cause a decrease in the force of attraction between two magnets.