Since Sarah "found it hard to recall when the pain began," we can infer that she must not know what caused her injury. The context clue in this sentence is noting that Sarah does not know the origin or "source" of the pain and when it began. This is opposite of the answer choice "ending." Also, "intensity" is the relative degree of something; "difficulty" is complexity; and "severity" is the degree to which something is severe in comparison to other things.

When people learn together, they often must cooperate. As a result, team is a good fit for this sentence because teams must work together and collaborate. 

We can infer that because the sentence refers to "climbers" who "placed a flag on [the mountain's] highest point" after they "made it all the way to the top," we need to pick out an answer choice that means something like "the top of a mountain." Neither "bottom" nor "valley" can be the correct answer, then, because each of those terms are antonyms of "top" and "mountain," respectively. "Summit," however, when used as a noun, means " the highest point of a hill or mountain," and because "summit" best fits the context of the sentence, "summit" is the correct answer.

We can infer that we need to pick out an answer choice that means something like "conditions," because the club "lost several members who did not meet the new conditions." "Requirements" is a noun that means either "things that are needed or wanted" or "things that are compulsory; necessary conditions," and because "requirements" best fits the context of the sentence, "requirements" is the correct answer.

The key to the sentence is noting that the introduction being referred to came before the first chapter.  Therefore, it is a foreword or prologue.

We can infer that we need to pick out a noun for the blank that means something like “a series of games.” So, while “game” may look like a potentially correct answer, “game” cannot be the correct answer because the sentence says that there were “many rounds of games.” “Tournament,” however, is a noun that can mean “a series of contests between many teams or players,” and because “tournament” best describes the series of basketball games that the sentence is discussing, “tournament” is the correct answer.

The correct answer is "precipitation," which means water that falls from the sky in a liquid or solid form. "Precipitation" is the only answer choice that can ruin a picnic but is also needed to help plants grow. "Wind" and "ants" can ruin a picnic, but they do not directly help plants grow. "Sunlight" helps plants grow, but it is not something that will ruin a picnic.

The prefix "cent-" means one hundred, so a period of one hundred consecutive years is a “century.” To provide additional help, a “decade” is a period of ten consecutive years; a “millenium” a period of one thousand consecutive years, and a "dozen" twelve units of something taken as a group.

In this sentence, we know that Lisa acts immaturely. This means that she acts younger than her age at time. Since she is thirteen years old, the blank should be filled with a word that means someone who is younger than thirteen. An "infant" is a very young child, much younger than thirteen. Therefore, "infant" is the correct answer.

Here, the sentence provides enough context for the reader to realize that the dog is searching for his bone and was not successful in finding it. Therefore, it is the dog's "search" that is "fruitless" (ineffective). It would not make sense for his "hope," "desire," "appetite," or "bowl" to be fruitless.