Solution

A-F is the correct pairing. A ("The research sought to decipher how brains...") is an independent clause that introduces the subject of the research. F ("are wired and the signals underlying healthy brain functions") completes the thought and adds detail about what the research aims to understand. Together, they form a coherent and grammatically correct sentence: "The research sought to decipher how brains are wired and the signals underlying healthy brain functions." Other options either do not form correct pairs or are incomplete.