A student investigated the rate of decomposition of two different types of fruit peel. The student placed 50 g of chopped banana peel in a mesh container. They placed 50 g of chopped apple peel in an identical mesh container. Both containers were left in the same location in a school greenhouse. The mass of the peel in each container was recorded every 7 days for 6 weeks.
State two variables that would need to be controlled in this investigation to ensure a valid comparison.
