The Law of Conservation of Matter States That Matter Cannot

The law of conservation of matter states that matter cannot be created, yet matter is sometimes gained or lost to an ecosystem. What is the reason for this seeming contradiction?

A) Chemoautotrophic organisms can convert matter to energy.
B) Ecosystems are open systems; therefore, matter can be moved in/out of an ecosystem from/to another ecosystem.
C) Photosynthetic organisms convert sugars to more complex organic molecules.
D) Detrivores convert matter to energy.
E) Heterotrophs convert heat to energy.