Answer:
Correct answer is It was held in secret.
It originally met to write a whole new Constitution.
Step-by-step explanation:
It was held in Pennsylvania State House, therefore it met in Philadelphia.
Only Rhode Island didn't sent its representative, therefore representatives of 12 states were present.
Of course, it was not held in secret as states had to choose their representatives before sending them.
Its purpose was not to write new Constitution, but to amend Articles of Confederation.