Given a disfluent sentence, modify the sentence to it to its equivalent fluent form, preserving the meaning of the sentence.

Example input: Who did the Han Chinese want to help the Khitan no I mean the Mongols fight?
Example output: Who did the Han Chinese want to help the Mongols fight?
Example explanation: The input initially means Khitan and then changes to Mongols, hence this is correct.
Q: Evolution of which or no make that of what part of the immune system occurred in the evolutionary ancestor of jawed vertebrates?
A:
Evolution of what part of the immune system occurred in the evolutionary ancestor of jawed vertebrates?