Final answer:
The elementary body of Chlamydia trachomatis is the extracellular, infectious form that is not permeable to metabolites and nutrients outside the host cell, making option A) the correct choice.
Step-by-step explanation:
The elementary body of Chlamydia trachomatis is known as the extracellular, infectious form of the bacterium, which is metabolically inactive until it enters an epithelial cell of a host organism. Once the elementary body is inside the host cell, it transforms into an active reticulate body that multiplies using the host cell's resources. Specifically, the elementary body is not permeable to metabolites and nutrients because it is not metabolically active outside the host cell. Hence, the correct answer is A) It is the extracellular, infectious form. This feature helps the pathogen survive outside of the host cell until it can find access to another host. Options B), C), and D) do not describe the characteristics of the elementary body of C. trachomatis.