Subject of a "that clause" ?

Hi~ In the following paragraph, what could be the best possible subject of the "that clause" underlined below?

1) A wide range of knowledge

2) The activities of genius -- learning a wealth of information in one area, and being able to make sophisticated associations from a wide range of knowledge ?

Thanks for your help in advance~

----------

Studies on individuals who became accomplished in their chosen
fields reveal that early exposure along with high amounts of repetition of
related core information as compared to their peers was the key difference.
Genius is nothing more than learning a wealth of information in one
area, and then being able to make sophisticated associations from a
wide range of knowledge that results in the bringing of two ideas together
that no one had previously connected.