The amount and kind of melanin present in the cortex and medulla of a hair shaft determines hair color. When melanin is replaced by air bubbles in the shaft, which is the resulting hair color

just finished the test, the answer is d, greg is the least cost-effective because he charges the most for the project

it's diluted or concentrated

in a diluted solution, you can add a lot more solute but in concentrated only a little more can be added