What does the term focus refer to?
a. an earthquake with a magnitude over 10.0
b. the spot inside earth where an earthquake occurred
c. the spot on earth's surface above an earthquake's origination point
d. a location on earth that suffers the most damage as a result of an earthquake

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.