Here's an example that might help you understand the difference between the noun "subject" and the verb "subject". Imagine a country that has a king. The people he rules over, the citizens, are called his "subjects" (noun). The king "subjects" (= "rules over") his subjects. The subjects are "subjected" to his rule. So, when you say "a person subjects his options to scrutiny" it is like you are saying the person is like the king, and his options are like the citizens over whom he rules. It means the person exercises control, using scrutiny, over his options.

In this sentence, 'subjects' means 'causes to undergo'. A person who uses critical thinking causes all available options to undergo scrutiny and skepticism. You could also use 'exposes' instead: A person who uses critical thinking exposes all available options to scrutiny and skepticism.

This is fairly formal, academic, written language. The verb "to subject" can mean "to put something under one's power." For example, some dogs don't like to be washed, and you might say "He subjected the dog to a bath." In a monarchy, a queen rules over her "subjects." A person who uses critical thinking examines every fact and every assumption. They check every fact. They challenge every assumption. "Scrutiny" means close examination. A critical thinker put everything under a microscope. There is also a verb form, "to scrutinize." You could say "A critical thinker examines everything." You could make it stronger: "a critical thinker scrutinizes everything." Stronger yet, you could say "a critical thinker puts everything under scrutiny." Or you can suggest that the thinker is being active, is dominating the facts, is forcing them to be examined: "a critical thinker subjects everything to scrutiny."

If you think critically, you apply scrutiny and skepticism to all available options.

I am not native but I think it used as "observe, survey and investigate" subjects all available options , survey all available options. does it make sense? I hope my idea will gonna help you! ;)