I want to make sure I'm identifying the antecedents correctly in the following sentence. The exercise itself calls for identifying the proper pronoun and then identifying the antecedents.

The sentence is:

"One survey indicates that Missouri, along with 12 other states, finds that (they, it) (I chose they) must provide remedial education for (their, its) (I chose their) government workers."

I said that Missouri and states are the antecedents. Am I correct in identifying states as an antecedent? I believe "Missouri" and "states" to be the compound subject in the sentence.

Thanks for clarifying!
Additional phrases that appear to form compound subjects don't really count toward the formation of a plural. For example,

The chairman, as well as the treasurer, feels that the cost will be too high. (not feel)

So you'll need to ignore "along with 12 other states" and write

... Missouri, ..., finds that it must ... for its ... workers.

Jim is right.

If the sentence had started 'One survey indicates that Missouri and 12 other states find that they must ... for their ... workers', then you could consider 'Missouri and 12 other states' the plural subject of the sentence.

Site Hint: Check out our list of pronunciation videos.
OP here -

Thank you Jim and Rover for sorting that out for me. It gets confusing after awhile when you have been working on homework for a long time and everything seems to be like the right answer, Emotion: smile.

Off to correct my mistakes!
Teachers: We supply a list of EFL job vacancies