The correct answer is - d.) to understand religion's effect on the physical environment.
The religion is a very important thing in the daily lives of billions of people all around the world, and thus it is a very important factor in the behavior of the people that follow a certain type of religion. Because the religion is so important and involved into the human's lives, it is an important factor in the anthropological shaping of the physical environment because every religion has it's institutions that require building space, they have different shapes of warship, some of which are positive towards the environment, while others are very destructive. Because of this the geographers are studying its effects and to see how it affects the environment, and how can it be managed and improved.