Which is a change early farmers made to their environment?
a. they planted orchards.
b. they burned undergrowth.
c. they created terraced farming.
d. they built dams.

The correct answer will be option- B.

Explanation:

The main aim of the farmers has always been to increase the productivity of the main crops grown in their fields. They always tried to develop the techniques and practices which could help increase productivity.

One of the practices performed by the earlier farmers which is still practices today is to remove the undergrowth or the weeds or the unwanted vegetation that inhibit the growth of the main crops.

To remove this they used to burn the weeds and small plants which provided two main benefits to the farmers: cleared land for farming as well increased the concentration of nutrients to the soil.

Thus, Option-B is the correct answer.