When a solution of cesium chloride (CsCl) is subjected to high-speed centrifugation, a stable density gradient is formed. Meselson and Stahl found that when cell contents were subjected to centrifugation with a CsCl solution, a band of DNA formed at the CsCl density that matched the density of the DNA. This technique is called density-gradient centrifugation. The test tubes below show the results of density-gradient centrifugation of five different DNA samples. Assign letters a-e to the pictures above. A) DNA from E. coli cells grown in ^5N B) DNA from E. coli cells grown in ^14 N C) A 1: 1 mixture of DNA from cells grown in 14^N and cells grown in ^15 N D) A 1: 1 mixture of DNA from cells grown in 14^N and 15^N, heated (to disrupt hydrogen bonds) and cooled (to allow reannealing) E) DNA containing one strand of ^15 N-DNA and one strand of ^14 N-DNA