open on principle / open system

open trial system

vexation / regret / chagrin / be chagrined / be regretful / be vexed

be attached to / regret / feeling attached to / be penitent for / being penitent for / affection / be unmanly / feel attached to / attachment / being sorry for / repent of / feel reluctant / looking back on with regret / being attached to / feeling regret for / reluctance / regretting / be sorry for / feeling reluctant / repentance / look back on with regret / being unmanly / feel regret for / with a bad grace / repenting of

opening *something to the public / make *something public / making *something public / open *something to the public

the world / common / ordinary / the people

guidance given outside the school

betray / mention / divulge / disclose / leak (a secret) / reveal / tell

the Environmental Pollution Prevention Act

optical isomerism