Which example violates the free-exercise clause?

The answer choices are:
 a.) Allowing a school to run weekly prayer sessionsb.) Allowing a student to wear religious clothingc.) Stopping a religious group from praying on the White House lawnd.) Stopping a religious group from buying a building based on their faith

Correct answer choice is:

c.) Stopping a religious group from praying on the White House lawn
Exercise Clause is the section of the 1st Amendment. According to the exercise clause, Congress was forbidden to make any law which may support the establishment of religion or which may prohibit the free exercise.