Here's a problem to solve: Each student in Ms. Jordan's science class was given a beaker containing several substances that had been stirred thoroughly. Maxwell must classify the contents of his beaker as either a compound or a mixture. Which of the following would indicate that the beaker contains a mixture?

Among the 4 following options, which is the correct answer?

- A: The original substances had different densities.
 
- B: The contents of the beaker reacted to form a new substance.
 
- C: The original substances had a greater mass than the contents of the beaker.
 
- D: The contents of the beaker can be easily separated into the original substances.
 