This is an age old tool used to crush seeds -

The mortar is filled with the bajra cobs (okhli, used for crushing). The seeds are extracted from the cobs after they have been crushed with a pestle (moosli). These days, large equipment like threshers carry out this labour. The seeds are crushed using one of two different processes. Using a mortar pestle is an age old approach, while using machines is a recent one.

Therefore, the correct answer is an option (C).