C. testable and observable
Scientists are preserving the DNA for research.
Some signs of a chemical change are a change in color and the formation of bubbles. The five conditions of chemical change: color chage, formation of a precipitate, formation of a gas, odor change, temperature change.
The best answer in terms of how organ cultures are an improvement on this transport method is "<span>Cultured organs can be kept alive for several weeks before transplant."</span>