Standard non-defining usage: select all sentences that are grammatical as written.
The mayor, that opened the fair, left at noon.
Lena, who designed the poster, joined us.✓Correct answer
Our oldest camera, we bought in 2012, still works.
We missed the train, which changed our plans.✓Correct answer
Explanation
The sentence about Lena correctly uses who for a named person, and the missed-train sentence uses which to comment on the whole event. The mayor sentence is the closest distractor because that is excluded from comma-set non-defining clauses.