In A one can see in these bars 4 minor crossings-out. All concern cautionary accidentals that Chopin, after a moment of reflection, considered superfluous. The accidentals in the L.H. part – 
before c
in b. 490 and 
before B in b. 491 – warn us not to play notes peculiar to the G minor key, which is going to be confirmed only just in the next bar.
Compare the passage in the sources »
category imprint: Corrections & alterations; Source & stylistic information
issues: Cautionary accidentals, Deletions in A
notation: Pitch