Which of the following statements is true of an open system?

A) There is an exchange of energy only with the surroundings
B) There is an exchange of matter only with the surroundings
C) There is an exchange of both matter and energy with the surroundings
D) In an open system either matter or energy, but not both may be exchanged with the surroundings
E) Energy flows only into the system: matter flows out of the system