What is the purpose of the establishment of clause

B. to stop government from supporting one religion

Establishment Clause doesn't allow the government to make any official religion.

Explanation:

In "United States" law, the "Establishment Clause" of the "First Amendment to the United States Constitution", along with "Amendment's Free Exercise Clause", together creates the constitutional right of "freedom of religion".

"Establishment Clause" restricts the government from forming any "law" that would respect establishing a religion. It also stops the government from preferring a particular religion over another. People can make their own lawful decisions. Government cannot promote any religion. But this doesn't mean that it restricts the government from placing religious symbols in its premises.