In mycoplasma, the elementary cell body performs the function of

The correct option is reproduction.

Mycoplasmas are unique, wall-less bacteria known to be the smallest free-living microorganisms. Their life cycle is complex and involves multiple morphological forms.
During their reproductive cycle, Mycoplasmas form small, spherical structures known as elementary bodies (or elementary cell bodies). These elementary bodies are typically formed by budding or fragmentation of the parent cell.

Once formed, these elementary cell bodies act as the primary reproductive units. They eventually grow and develop back into mature vegetative cells. Therefore, in Mycoplasma, the primary function of the elementary cell body is reproduction.