Explain the function of a combine harvester.

A combine harvester is a crucial piece of agricultural machinery designed specifically for the harvesting of grain crops. Its primary function is to efficiently cut down the plants, separate the grain from the chaff and straw, and then clean the grain for storage. This process combines multiple steps—cutting, threshing, and winnowing—all into one machine, which significantly reduces the time and labor required to harvest crops compared to traditional methods.

The design of the combine allows for the simultaneous collection and processing of the harvested material. As the machine moves through the fields, it uses sharp blades to cut the crops, after which an internal mechanism separates the edible grain from the inedible parts. This efficiency makes it integral to modern farming practices, allowing farmers to cover large areas quickly and with minimal manpower.

In contrast, the other options pertain to different agricultural functions: collecting soil samples is typically performed with specific equipment designed for soil testing; preparing fields for planting involves tillage and other processes to ready the land, which are not functions of a combine; and fertilizing the soil during harvest is not a standard feature of combines, as their focus is on harvesting rather than applying nutrients. Therefore, the function of a combine harvester is accurately represented as efficiently harvesting grain