Rewrite the sentence in direct speech.
Prabhu said that he was not going to college.

Correct option is B

"He was not going to college" in indirect speech is correctly converted to "I am not going to college" in direct speech, reflecting the present continuous tense to discuss an immediate or future plan.
Rule of Conversion: Past continuous referring to a future plan in indirect speech becomes present continuous in direct speech. Pronouns change to match the speaker's perspective.
Example: He said he was going -> He said, "I am going."