Valerie creates a model using three different rocks. The rocks are classified as igneous, metamorphic, and sedimentary. Which property does Valerie use for classification purposes?

color
formation
shape
texture

Consider a culture medium on which only gram-positive organisms such as staphylococcus aureus colonies can grow due to an elevated nacl level. a yellow halo surrounds the growth, indicating the bacterium fermented a sugar in the medium, decreasing the ph as a result and changing the color of a ph indicator chemical. this type of medium would be referred to as a differential and enrichment culture.