How did Davis demonstrate that bacterial cells must be in physical contact in order for genetic exchange to occur?

Question

A. He mixed together two bacteria strains with different nutritional requirements, and then added them to agar plates that lacked their required nutrients.
B. When two bacterial strains with different nutritional requirements were combined in a tube and allowed to grow for several hours, they acquired the ability to grow without the addition of biotin.
C. When two bacterial strains with different nutritional requirements were separated from each other by a selective filter, they did not acquire the ability to grow on agar plates that lacked their required nutrients.
D. Only when enough pressure was applied to force bacteria from one side of a selective filter to another did they acquire the ability to grow without their required nutrients.
E. Nutritional deficient strains only acquired the ability to grow without their required nutrients when the pore size of a selective filter was increased to allow bacteria to pass from one side to the other.

Answer 1

C. When two bacterial strains with different nutritional requirements were separated from each other by a selective filter, they did not acquire the ability to grow on agar plates that lacked their required nutrients.