Given a scientific question, generate a correct answer to it.
--------
Question: The fetus is connected to what by a tube called the umbilical cord?

Answer: placenta

Question: A problem with using food chains to describe ecosystems is that some organisms can feed on or be consumed by species from more than one of what level?

Answer: trophic level

Question: Which branch of science is the study of energy, matter, and their interactions?

Answer:
physics