<span>The pronoun "it" corresponds with the antecedent "glassmaking." If we replace the pronoun "it" with the suspected antecedent, we will be able to tell if we are correct: "Glassmaking was an honorable profession, but glassmaking could also be dangerous." Because this makes sense and retains the original sentence's meaning, we know that the pronoun "it" correctly corresponds to the antecedent "glassmaking."</span>
While it is true that the word "glassmaking" is an antecedant of the pronoun, the pronoun itself does not refer specifically to it. Instead, the pronoun reffers to "profession": an antecedant is typically the previous, <em>immediate </em>noun or phrase that a pronoun refers to. Whereas the word profession is standing for galssmaking, it is not the latter the one referenced by the pronoun.
Both the first one and the last one could be correct here, but choosing which one is best would probably be the last one becasue the biggest difference, or what sets the two apart is primarily who is around.
