Given a statement, generate a question such that the answer is contained in that statement.
--------
Question: individual nerve cells transmit nerve signals to other cells.

Answer: What transmits nerve signals to other cells?


Question: some predecessors became more mammal-like as they continued to evolve

Answer: What did some predecessors become?


Question: the virus that causes smallpox is another potential threat in the atmosphere

Answer:
What is another potential threat in the atmosphere?