A part of the periodic table is shown. A portion of the sixteenth and seventeenth columns of the periodic table is shown. Column 16 reads eight oxygen, 16 sulfur, and 34 selenium. Column 17 reads nine flourine, 17 chlorine, and 35 bromine. (there is also a pic)

Which of the following elements is less reactive than the others?

Bromine (Br)
Oxygen (O)
Selenium (Se)
Sulfur (S)

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.