A student investigated the decomposition of two different types of organic waste.
The student placed 50 grams of apple slices in a mesh tray.
The student placed 50 grams of banana slices in another identical mesh tray.
Both trays were left in the same location inside a school greenhouse.
The mass of the waste in each tray was recorded every 3 days for 15 days.
State two variables that would need to be controlled in this investigation.
