Final answer:
Rusty is sharing a discovery that Ariel's dad has made; Ariel was caught by her dad coming home from the Bar-B-Que, indicating that this was an unexpected or unapproved action.
Step-by-step explanation:
Rusty is sharing a discovery. In the sentence provided, Rusty exclaims to Ren that Ariel's dad caught her coming home from the Bar-B-Que. This implies that Ariel's dad has discovered something about her actions, specifically her return from the Bar-B-Que, which likely was not expected or approved. Therefore, the news Rusty is sharing corresponds to Option C: A discovery.