Organ donation rates are rising in the United States, but they haven't kept up with demand. More than 50,000 people are awaiting kidney transplants alone, according to the United Network for Organ Sharing. One reason for the shortage is the difficulty in transporting donated organs to where they are needed. Because of the primitive way organs like kidneys are currently shipped-in plastic containers filled with ice and suspension fluid-they can remain only viable for about 20 hours.

Select from the choices above to read the entire article.