The peas haven't start germinating, which means no leaves. They can't undergo photosynthesis to produce oxygen. At this stage they are still undergoing respiration, which produce carbon dioxide.
They have the same mass as the mass of the reactants. evidence to back this up is the law of conservation of mass
Water falls from a reservoir through a channel to a turbine. The water turns the turbines, which allows the generator to make electricity.
It's both! Scientists really can't agree on it.
