Which statement is true about energy changes?
a. energy can be created but not destroyed.
b. energy can be created and destroyed.
c. energy can be destroyed but not created.
d. energy cannot be created or destroyed.

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.