Infinitive as adverbial modifier of purpose

Question

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).

Answer 1

Your question is specific to the example:

To Understand (a) electricity (b) depends (c) on a knowledge of atoms and the subatomic particles of which they are composed (d).

In this version, "To understand" is trying to communicate "In order to Understand". So if I wanted to define the message of this sentence. In order "To Understand electricity" I must depend on the knowledge of atoms and the subatomic particles of which they are composed. It essentially sets a goal within the definition. My goal "Is to understand electricity", to do that I must gain the essential knowledge of atoms and subatomic particles.

Answer 2

As a learner:

"To understand electricity" is an infinitive clause. The infinitive clauses can take on the roles of a noun, or in other words you can treat them like a big noun when they are used as the subject!

One form of making an infinitive clause is using "to + infinitive" pattern as the subject. For instance,

To love and to be loved are the main things that make everyone happy.

or

To fix this issue is my biggest concern now.