This very short sentence requires you to be very careful about clues. Notice the word "trembled." Whenever something "trembles," it shakes. Now, don't be tempted to think that the string must be thin or small just because it is shaking. All we know is that it is shaking. Swinging things can be said to shake in some way. "Vibrating" is a better synonym for "shaking" than is "swinging."

On your own, you would likely choose a word like "annoyed" to describe Lawrence's state of mind. Since this is not an option, you need to have another word that expresses his slight anger. The word "irritated" does just this. When we "irritate" someone, we annoy him or her. An "irritation" is a minor annoyance. Gerard's clicking teeth were just a minor irritation for Lawrence, nothing more.

Pay attention to the contrast that is expressed in this sentence. Thomas's pain must not be too bad right now. The two clues that help you to see this are "although" and "only." We don't know much about the particular kind of pain that he experiencing. By knowing that it is not bad, we know that it is "moderate."  

The general idea is that the person involved will ultimately overcome her difficulties and achieve her desired goals. When we overcome difficulties like this, we "prevail over them." None of the other options express this idea of "conquering" difficult so as to achieve our goals.

The only thing that you know is that the person in question is being described as "unwilling." We do not know if he or she is afraid to do the task (or really anything more detailed than "unwilling"). Therefore, the best answer is the one that stays closest to this basic meaning. When we are "reluctant" to do something, we are hesitant or unwilling. Since this is as general of a meaning as that which is indicated by your clues, it is the best option.

The idea that is presented here is that Lawrence is very devoted to the opera. He is not just a partial supporter of it. No! He does everything he can to support it—asking friends, giving money, and giving time. Although he might be wealthy, the point that the sentence is trying to express about him is that he is very "enthusiastic" about the opera.  

The issue here is one of fairness. The store owner does not want to overcharge, which implies that he has some idea of a fair price that he should charge for his goods. When we act fairly, we act with justice. Something that is "fair" can be called "just."

Since Heidi is upset because of her brother's actions, it probably means that her brother aggravates or "antagonizes" her. The other answer choices mean the following: "soothe" means calm; and "encourage" means support. "Interrupt" and "tease" are tricky choices. While it might bother and annoy someone to be teased or interrupted, we are told that Heidi's younger brother specifically steals her favorite stuffed animal, which isn't "teasing" or "interrupting." So, "antagonize" is the best choice because it is a more general word.

In this sentence, it is made clear that the student has an excess of energy and as a result is pacing about his room. This indicates that he is "restless," meaning that he is not able to relax himself. "Restless" is therefore the best way to complete this sentence.