Do not be tempted to pick words like "industrious," as though this sentence were contrasting "dull, unimaginative" with "hard-working." Instead, "dull, unimaginative" should be contrasted with something indicating imagination and a kind of flair or ability. The best option for this is "creative," for people are creative when they are not dull or unimaginative.

The contrast here is between advanced and difficult topics and ones that are not advanced or so difficult. The idea is that you must first finish the basics before moving on to the more difficult aspects of a topic. The "elements" of something are its most basic parts, so the word "elementary" means pertaining to the basic parts. "Elementary school" gets its name from this, for it means "the school where the basics are learned."

To answer this question, stay as close to the sentence's meaning as possible. Thomas is said to be "relatively confident." That means that he is not completely sure about his answer, but has some certainty. To be "certain" without any other limitation is to be sure. This best fills the direct meaning that we need. While someone who is confident might brag, we are told nothing that should lead us to think that is the case with Thomas.

The main clue in this sentence is the expression "but when he actually would do so." The implication is that John did not eat peas very often. When he did, he ate a lot, but that was not very frequently. Therefore, he ate them "seldom," an adverb meaning rarely. This best expresses the idea that he did not eat peas very often. Notice that the word "seldom" is an adverb even though it does not end in "-ly" like most regular adverbs.

We do not know anything about Peter's specific painting style. For that reason, we should ignore "Impressionist" immediately. The option "amazing" might be tempting, for peter was able to paint with little training and practice at all. However, the idea that is stressed by the expression "with little practice at all" is that he seemed to have the ability to paint almost as if by nature. Therefore, the best option for our purposes will be "natural." A "natural painter" is someone who seems to have his or her abilities "from nature," that is, without any training or practice (as if he or she was born with it). Indeed, the word "nature" comes from the same Latin word that gives us "nativity" and "natal"—both words related to being born.

The key description that we have for Bill is his "crazy" lifestyle. In contrast to this, he has decided at last to "settle down," meaning that he has decided to live a calmer life. When one is "sensible," that person is practical and prudent. A "sensible" set of actions is one that is level-headed—far indeed from being "crazy."

The implied contrast in this sentence is between "optional" and our blank. The word "optional" means "not necessary." When you have many options, it is likely not the case that any one of them must be chosen. In contrast to such "optional" things, the cleaning must be completely "necessary" for Laura. Therefore, this is the best option. Even "joyful" is not good enough, for we do not know whether or not cleaning is a source of joy for her. We only know that it must be done.

A mystery requires a lot of attention paid to all the details involved. Therefore, when you "probe" (that is, look into) them, you must consider them very carefully. The adverb "thoroughly" best fits this description. When something is "thorough", it is complete—as though it "goes through" everything. A "thorough investigation" is one that sifts through all the details with great care and depth.

The sentence opens by explaining the natural state of human life. Most people need seven to eight hours of sleep (at least according to this sentence). The word "although" indicates a contrast between these "normal" humans and those needing less sleep. While we might think that such sleep patterns lead to sickness, we cannot assume this is what the author wishes to express. All we know is that he or she is contrasting normal and abnormal patterns. Therefore, the safest answer is "unnatural."

We cannot be sure how the boundaries of the playground are marked. (Therefore, we cannot choose either "chalked" or "gated.") We do know, however, that the boundaries must appear rather obvious. There is "no doubt" if someone goes too far beyond them. Since there is no doubt, they must be rather "definite", meaning that they are clearly and well defined. Something "indefinite" is lacking such clarity (and is, perhaps, even "nebulous").