The first alternative is correct (A).
The confederation is an association organized by sovereign states, which may eventually adopt a common constitution. This is exactly the case in the USA.
The American Constitution has been proclaimed so that there is a central government capable of dealing with common demands of states, such as international representation and wars. However, each state has its territorial independence, that is, the central power is relatively limited.
The constituents wanted to avoid the abuses they perceived in the absolutist monarchies that had a strong central government. In this way, federalism was the ideal way to build a unity, while maintaining the independence and power of states.
