Question

the extract of which gymnosperm seed is used to help improve memory? ephedra cycad ginkgo pine tree

Explanation:

Ginkgo (Ginkgo biloba) is a gymnosperm, and its seed extract (ginkgo biloba extract) is known for potential memory - improving effects. Ephedra is mainly associated with stimulant properties, cycad seeds are toxic and not used for memory improvement, and pine tree seeds don't have a notable role in memory enhancement.

Answer:

C. ginkgo