( ( All borders ) ( ( can ( be ( ( ( divided ( ( into seven ) ( ( -LRB- ( ( only seven ) -RRB- ) ) ( symmetry classes ) ) ) ) , ) ( according ( to ( whether ( ( the ( repeating pattern ) ) ( would ( be ( unchanged ( under ( specific ( possible operations ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT All) (NNS borders)) (VP (MD can) (VP (VB be) (VP (VBN divided) (PP (IN into) (NP (CD seven)) (NP (PRN (-LRB- -LRB-) (NP (QP (RB only) (CD seven))) (-RRB- -RRB-)) (NN symmetry) (NNS classes))) (, ,) (PP (VBG according) (PP (TO to) (SBAR (IN whether) (S (NP (DT the) (JJ repeating) (NN pattern)) (VP (MD would) (VP (VB be) (ADJP (JJ unchanged) (PP (IN under) (NP (JJ specific) (JJ possible) (NNS operations))))))))))))) (. .)))
All borders can be divided into seven (only seven) symmetry classes, according to whether the repeating pattern would be unchanged under specific possible operations.
(ROOT (S (NP (NNS Mollusks)) (VP (MD can) (VP (VB be) (VP (VBN divided) (PP (IN into) (NP (CD seven) (NNS classes)))))) (. .)))
Mollusks can be divided into seven classes.