I read this sentence in the Barron's practice exercises book (you should choose the incorrect usage):
The understanding (a) electricity (b) depends (c) on a knowledge of atoms and the subatomic particles of which they are composed (d).
The incorrect part is (a) and I should replace it by Understanding or The understanding of. But the book also suggests using To understand form as a correct answer.
Could you explain to me if it is possible to use the last one in that particular case?
I don't completely understand it (hope my misunderstanding is set clearly).