(a) Left over food can be collected and used to make compost. Compost provides nutrients essential for the growth and development of plants.
(b) We would prefer to eat food in a banana leaf plate. This is because a leaf plate is a harmless substance that can be used to make manure by the process of composting, whereas plastic plates cannot be converted into harmless substances by composting. They are not degradable so remain in the environment and create many problems.