Final answer:
Niger is the country that is bordered by both Burkina Faso and Libya.
Step-by-step explanation:
The country bordered by both Burkina Faso and Libya is Niger. Mali is incorrect as it is bordered by Burkina Faso but not by Libya. Chad is bordered by Libya but not by Burkina Faso, and Sudan is not bordered by either of the two countries. Therefore, the correct answer to the question which country is bordered by Burkina Faso and Libya is b) Niger.