Which example violates the free-exercise clause? - allowing a private coming to run weekly prayer sessions - allowing a student to wear religious clothing - stopping a religious group from praying on the white house lawn - stopping a religious group from buying a building based on their faith

The answer is: stopping a religious group from buying a building based on their faith

The free exercise clause allowed citizens of united states to freely adopt whatever religion that they believed in, as long as they are not hurting other citizens.

Stopping a religious group to buy building based on their faith is a direct interference to the people who want to freely devote themselves to their religion. This can be seen as a direct violation to the free exercise clause.