Pretty sure the answer would be C, because you need the warm and cold air to mix.
Answer: Mixture
Explanation:
If there is and unstable element composition of say, pure graphite an un-pure gold then a chemical reaction will most likely be used to separate the two elements.
Answer:
CCCATG
Explanation:
A complements with T and Vice versa
C complements with G and Vice versa
Temporary changes would be weather, since it can change at any givin time another example would be tides coming in because they vary by day, or wet sand becoming dry sand!
