I had the same question, it's most likely B.
Mixtures of sand and water or sand and iron filings, a conglomerate rock, water and oil, a portion salad, trail mix, and concrete (not cement).
No, darker colors like purple and blue have higher wave frequency which transmit more energy.
Compounds are classified according to the elements that make them up. For example, oxides contain one or more oxygen atoms, hydrides contain one or more hydrogen atoms.
compounds form different types of bonds too. a metal and nonmetal element will create an ionic bond, two nonmetal elements create covalent bonds