Starting in 1945, Escherichia Coli Became a Bacterium of Choice

Starting in 1945, Escherichia coli became a bacterium of choice to study basic cellular processes and gene function. What specific feature of E. coli is responsible for its rise to prominence as a model system?

A) very fast growth rate
B) ability to grow in suspension culture and on agar plates
C) ability to transfer a copy of a plasmid from one cell to another
D) the fact that it has small, circular DNA