Answer:
open system
Coffee held in a cup is an open system because it can exchange matter water vapors and energy heat with the surroundings.
I've considered it answer
Hmm, I am not quite sure but if I am probably your best bet so I'd go with, either B or D.
Answer:
It's C
Protons repel the neutrons.
Explanation:
An atom is unstable (radioactive) if these forces are unbalanced; if the nucleus has an excess of internal energy. The instability of an atom's nucleus may result from an excess of either neutrons or protons.
Answer: A. It reflects sunlight
hope this helps let me know if it's wrong