Concept:A combine harvester is a single machine that performs multiple harvesting tasks for grain crops at the same time.
Explanation:A combine harvester combines reaping, threshing, and winnowing in one operation.
It is mostly used for cereal crops such as wheat, maize, and rice.
These three actions together allow the machine to harvest mature grains and also separate and clean them from chaff.
Therefore, it can harvest cereals and winnow grains simultaneously.
Answer:D. cereals and winnow grains