Option 1 -> Uses past perfect (had submitted) for the earlier action and simple past (started) for the later action - correct sequence for two past events.
Option 2 -> Present perfect tense for both actions doesn't fit the context of describing completed past events with a clear sequence.
Option 3 -> Mixing simple past (submitted) with simple present (start) creates grammatical inconsistency.
Option 4 -> Simple present tense for both doesn't suit the context of past events being described.
Hence, Option 1: had submitted, started -> When two actions occurred in the past, we use past perfect for the earlier action (submitting findings) and simple past for the later action (conference starting). The word "before" signals this sequence of past events. -> correct