Finish the following sentence with the best choice: To make a concrete sphere.

Choices:
- Take a spherical shell and spray with oil before pouring in the dry concrete into it. Allow to dry and set. Break the glass shell to remove the concrete sphere.
- Take a glass spherical shell and spray with oil before pouring in the mixed concrete into it. Allow to dry and set. Break the glass shell to remove the concrete sphere.

Answer:
Take a glass spherical shell and spray with oil before pouring in the mixed concrete into it. Allow to dry and set. Break the glass shell to remove the concrete sphere.