The mechanism for acid catalyzed transesterification was confirmed by using 18 O labeled ethyl butanoate and following the label. Sketch out a...

The mechanism for acid catalyzed transesterification was confirmed by using 18O labeled ethyl butanoate and following the label. Sketch out a plausible mechanism: where would you expect the 18O label to show up? 

A. Both oxygens of the resulting ester will have 18O incorporated

B. all three oxygens of the two products will have 18O incorporated

C. only the carbonyl oxygen of product ester will have 18O incorporated

D. only the -OH group of ethanol will have 18O incorporated