To which of the following is a modern seed drill attached?

A modern seed drill is a piece of agricultural machinery used for planting crops. It is designed to plant seeds at a precise depth and spacing in a single pass over the field. 

Modern seed drills are frequently mounted on the back of tractors. This allows for more efficient crop planting because the tractor can cover a large area in a short period of time. The seed drill can be programmed to plant seeds at specific depths and spacings to ensure proper growth.