The phrase "keeps sellers on their toes" in the passage mostly means "______".
Giải chi tiết:
Thành ngữ: keep sb on their toes (= to make sure that sb is ready to deal with anything that they are not expecting). "keep sellers on their toes" = makes sellers responsive to any changes: làm cho khách hàng sẵn sàng đáp lại bất kì thay đổi nào.