Whenever something is "profound," it is very deep and intensely influential. A "profound" feeling is a very deep feeling. The word "profundity" is a noun that describes something that has such a depth. For example, whenever someone says something that is very insightful and true, we say that he or she has expressed something of great profundity. This is the sense implied by the word in this question. Hence, you can say that he or she expressed something of "great depth"—speaking metaphorically, of course!

The word "pretence" is related to pretending, but do not confuse it with words like "conceptualize" and "imagining." Yes, when we pretend, we use our imaginations and our minds. The word "pretence," however, does more with making up something so as to be deceptive. A "pretence" is a fake appearance. For example, someone might have a kind of pretence that makes himself look more intelligent than he actually is.

The word "hindrance" quite clearly is related to the word "hinder," meaning to make more difficult. A "hindrance" is the very thing that makes matters more difficult. Therefore, it is a kind of obstacle that gets in the way. A "hindrance" can be either physical or more abstract. Thus, a tree in the middle of the road is a hindrance for travel. Emotions that are very strong might be hindrance in the way of someone accomplishing a given goal.

Perhaps you have used the word "epitome" without completely knowing its meaning. For example, you can say, "He was the epitome of kindness," or, "The book was the epitome of a depressing story." These expressions mean something like, "He was like a personification of kindness itself," and, "The book completely expressed the essence of a depressing story."

An epitome is the perfect kind of example or case of something else. Hence, the book was a perfect example of a depressing story, and the person was a perfect example of human kindness. Hence, the word "exemplar" works well. An exemplar is more than a mere example. It means a perfect example of something else. 

Perhaps you have heard an expression like "the annals of the king." Granted, the word is not the most popular of words today. It is used to describe the records that might be kept for a given year. Most often, it refers to the official records for that year—be they for a kingdom or for a modern nation. For this question, the only option that expresses this idea of having records is "archive." An "archive" is a stored set of documents for a given period of time about some particular thing or group.

Most frequently, you will see the word "tract" used in the expression "tract of land." A "tract of land" is a large piece of land of any kind. Hence, the best option among those provided is "expanse." Think of "expanse" as indicating an "expansive" piece of land. All of the other options pertain to this or that kind of land—inherited, only a field, etc. Only "expanse" captures the large size of a "tract" of land.

Perhaps you have heard the word "turbulence" in the context of flying. When an aircraft is experiencing bad winds mid-flight, the craft begins shaking, and the pilot will say that the plane is experiencing turbulence. This means that it is experiencing a disturbance. The word "turbulence" can apply to any kind of disturbance, not merely wind disturbances in a plane. It can also apply metaphorically to situations in which there are drastic unexpected changes to the normal state of things in a given field, e.g. "political turbulence" or "economic turbulence." Therefore, the best option is "upheaval," and not words like "aircraft," "gale," or "breeze."

A number of the incorrect options for this question try to get you to misuse your experiences at the dentist. If you have a cavity in one of your teeth, this likely occurred because of tooth decay; however, the "cavity" is not the decay process itself. Instead, it is the result of that process. It is the little hole in the enamel of your tooth. Therefore, the best option for "cavity" is the simple word "hole." Indeed, the word "cavity" can be used to describe any kind of hollow space, not merely the kind caused by tooth decay!

The word "trepidation" comes from Latin roots meaning to tremble. Whenever we say that someone is "full of trepidation," we are indicating that the person is disturbed and hence is likely trembling with fear or anxiety. The word can also be used to indicate the feeling of dread that causes such shaking. This is how it is being used in this question.

Perhaps you know the adjective "tumultuous." This describes someone or something that is very agitated and not at peace. The word "tumult" describes this state of affairs. In a rather obvious way, we can say, "A tumultuous person lives in a state of tumult." The word "unrest" is a combination of the prefix "un-", meaning not, and "rest." Whenever something is in a state of unrest, it is not at peace for sure! Hence, this word is a good synonym for "tumult."