Arrange the following events of Meselson and Stahl's experiment in order of their occurence:

A. DNA extracted from the culture, twenty minutes after transfer from ${}^{15}N$ to ${}^{14}N$ medium had a hybrid density.
B. E. Coli with heavy DNA were transferred into a medium with ${}^{14}NH_4CI$.
C. E. Coli were grown in a medium containing ${}^{15}NH_4CI$.
D. DNA extracted from the culture after forty minutes had equal amounts of hybrid DNA and light DNA.

Choose the correct answer from the options given below:

C, B, A, D

The correct answer is Option (4) → C, B, A, D