One way to describe the subject of a sentence is to use a

One way to describe the subject of a sentence is to use an infinitive...

Sorry if I'm incorrect Hope this helps you :)

One way to describe the  subject of a sentence to use an Infinitive

answer: the first one

explanation:

explicitly is defined as “in a clear and detailed manner, leaving no room for confusion or doubt.” the rest are interpretive and not clearly proven leaving in fact possible “confusion or doubt” which explicitly, by definition cannot have.