Which of the following contains a vague pronoun reference?

 - The recipe says to mix the black beans with the chopped tomatoes, but Scott forgot to buy them.
 - The recipe says to mix the black beans with the chopped tomatoes, but Scott forgot to buy the black beans.
The second answer choice contains a vague pronoun reference. The pronoun them could refer to the black beans or the chopped tomatoes.
The first answer choice shows a possible correction for the vague pronoun reference. Them has been replaced with the black beans.
The recipe says to mix the black beans with the chopped tomatoes, but Scott forgot to buy the black beans.