Why Is It Not Possible to Culture Treponema Pallidum in Vitro

Why is it not possible to culture Treponema pallidum in vitro?

A) The organism is an obligate intracellular parasite AND the organism is a psychrophilic anaerobe.
B) The organism is an obligate halophile AND the organism is highly motile and requires actin from host cells to make tails for movement.
C) The organism lacks mitochondria and obtains all of its essential macromolecules from the host AND the organism is Gram-negative.
D) The organism is highly motile and requires actin from host cells to make tails for movement AND the organism is Gram-negative.
E) The organism obtains most of its essential macromolecules from the host AND the organism is an obligate intracellular parasite.