Practice question

Question

RPMI and DMEM, supplemented with serum, antibiotics, glutamine and phenol red are routinely used for tissue culture of human cells in CO₂incubators. In addition, sodium bicarbonate (NaHCO₃) and HEPES are used as buffering agents. The following statements were made about the media. A. While 5% CO₂is optimal for cells cultured in RPMI , the optimal CO₂concentration for DMEM is 7.5-10%. B. HEPES is necessary if cells are to be kept outside the incubator in room air for long periods. C. NaHCO₃is necessary if cells are to be kept outside the incubator in room air for long periods. D. When cells grow rapidly in the culture medium for a few days, phenol red will turn the medium pink/red . Which one of following options represents the correct combination of all the statements?