_ASON
ON already proven
from BATON-3 we know that BAT (one of them is correct)
BOSON-3 we know that one of BOS is correct. The O is eliminated from COLON-2 (since ON are proven) leaving B_S one of the two being correct
BARON-3 shows that BAR one of is correct. Since BAT one of them is correct, T and R cannot both be right, so we are left with B or A.
BOLTS-0 proves that it is not B, so __S__ is correct and _A___ are correct from the above two reasonings