A) Materials are repeatedly used, but energy flows through and out of ecosystems.
B) Both material and energy are recycled and are then transferred to other ecosystems as in a flow.
C) Materials are cycled into ecosystems from other ecosystems, but energy constantly flows within the ecosystem.
D) Both material and energy flow in a never-ending stream within an ecosystem.
E) None of the choices is correct.

A) Matter is cycled through ecosystems; energy is not.
B) Energy is cycled through ecosystems; matter is not.
C) Energy can be converted into matter; matter cannot be converted into energy.
D) Matter can be converted into energy; energy cannot be converted into matter.
E) Matter is used in ecosystems; energy is not.

A) 1%
B) 10%
C) 25%
D) 50%
E) 100%