2.1 who are interested and want to learn more should extend the scope of the study, covering many fields, for example in the group by, you can compare the differences more clearly.
2.1 Those who are interested and want more studies should broaden the study to include samples in many fields. It will be able to compare the differences more clearly.
2.1 who are interested and want to study should further expand the scope of cover subjects in many districts. By comparing the difference will be more clearly.