Armed with invisible ink, a cipher system, and a passion to end the war and preserve the Union, Elizabeth Van Lew became Butler's eyes and ears in the Confederate capital city. Truth be told, however, she became much more than that. She became a spymaster, the person responsible for running a network of agents, couriers, and safe houses that was very active during the war. In addition to the spying, Elizabeth Van Lew continued to maintain her Church Hill home as a safe house and something of a local Union spy headquarters. —The Dark Game,
Paul Janeczko

The central idea that Elizabeth Van Lew was a spymaster is further developed. Which answer summaries the next central idea of the passage?

Van Lew’s roles and responsibilities were sometimes too much for her to bear.
Van Lew contributed to the development of systems and structures for spies.
Van Lew’s actions would not have been successful without the Church Hill home.
Van Lew’s educational background allowed her the skills needed to be a successful spy.

the answer is: Van Lew contributed to the development of systems and structures for spies .