You will be given a definition of a task first, then some input of the task.
Use a disfluent question or a proper question and find the answer to the question based on the given context or return None if an answer can't be found. A disfluent question is a question that has some interruptions in it while framing. A proper question is the correct form of the question without any disfluency.

proper question: What period did the emergence of feeding mechanisms come from?
disfluent question: What did er what period did the emergence of feeding mechanisms come from?
context: The early Cambrian sessile frond-like fossil Stromatoveris, from China's Chengjiang lagerstatte and dated to about 515 million years ago, is very similar to Vendobionta of the preceding Ediacaran period. De-Gan Shu, Simon Conway Morris et al. found on its branches what they considered rows of cilia, used for filter feeding. They suggested that Stromatoveris was an evolutionary aunt of ctenophores, and that ctenophores originated from sessile animals whose descendants became swimmers and changed the cilia from a feeding mechanism to a propulsion system.
Output:
None