I'm guessing the answer is a). I found a similar problem except if the bicarbonate was mixed with water instead. And the selections were: H3O(+), OH(-), CO3(2-), H2CO3 I think the answer to that question would be H2CO3 since it's asking for the conjugate acid which will be the form of bicarbonate when it accepts a proton. However, in the attachment, that question is asking for the conjugate acid when it is mixed in an acid. So water and carbon dioxide will be produced. and water is the one that accepts the proton. Am i correct? thanks.