6. Which of these is a run-on sentence?

A. You and I and the whole team will go.
[B. I thought about what he'd said soon I realized he was right.]
C. I went home and ate and ate.
D. Before lunch, I played volleyball; after lunch I did again.

Correct.

To identify a run-on sentence, we need to understand what a run-on sentence is. A run-on sentence occurs when two or more independent clauses are joined together without proper punctuation or conjunctions.

Looking at the options provided:
A. "You and I and the whole team will go." - This sentence is not a run-on sentence because it only contains one independent clause.
B. "I thought about what he'd said soon I realized he was right." - This sentence is a run-on sentence. It combines two independent clauses ("I thought about what he'd said" and "soon I realized he was right") without proper punctuation or conjunctions.
C. "I went home and ate and ate." - This sentence is not a run-on sentence. It contains one independent clause and uses conjunctions ("and") to connect the various actions.
D. "Before lunch, I played volleyball; after lunch I did again." - This sentence is not a run-on sentence. It uses semicolons to correctly separate two independent clauses ("Before lunch, I played volleyball" and "after lunch, I did again").

Therefore, the correct answer is B. "I thought about what he'd said soon I realized he was right."