पशु कोशिकाओं (animal cells) के संवर्धन के लिए उपयोग किए जाने वाले CO2 इनक्यूबेटर में आमतौर पर CO2 की कितनी सांद्रता रखी जाती है?

RPMI and DMEM, supplemented with serum, antibiotics, glutamine, and phenol red, are routinely used for tissue culture of human cells in CO 2 incubators. In addition, sodium bicarbonate (NaHCO 3 ) and HEPES are used as buffering agents. The following statements were made about the media: A. While 5% CO 2 is optimal for cells cultured in RPMI, the optimal CO 2 concentration 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. NaHCO 3 is 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 the following options represents the correct combination of all the statements?