Meaning: 'Brush up' means to improve your knowledge or skill in a particular area, especially after a period of not using it.

Wrong options:

• bring: 'Bring' implies carrying something to a place, which does not fit the context of reviewing knowledge.
• get: 'Get' is too vague and does not convey the specific action of reviewing or refreshing knowledge.
• take: 'Take' does not convey the idea of reviewing knowledge; it is more about receiving or accepting something.

Correct answer: Contrary

Explanation: 'Contrary' is the correct choice as it indicates a contrast to popular belief, fitting grammatically and contextually within the sentence structure.

Meaning: 'Contrary' means opposite in nature, direction, or meaning, indicating that the following statement will oppose common assumptions.

Wrong options:

• Opposite: While 'opposite' conveys a similar meaning, it does not fit grammatically as well in this context where 'contrary' is more idiomatic.
• Similar: 'Similar' suggests likeness, which contradicts the intended meaning of contrasting beliefs.
• Unlike: 'Unlike' is a preposition that does not fit grammatically in this context, as it requires a different structure.

Correct answer: an opportunity

Explanation: The phrase 'an opportunity' fits grammatically as it correctly uses the indefinite article 'an' with the singular noun 'opportunity,' indicating a single chance for viruses to spread.

Meaning: 'An opportunity' refers to a favorable chance or situation that allows something to happen, in this case, the spread of viruses.

Wrong options:

• chance: 'Chance' is a noun that can be singular or plural but does not fit the article usage required here.
• chances: 'Chances' is plural and does not match the singular context of the sentence.
• the opportunities: 'The opportunities' implies multiple specific chances, which does not align with the intended meaning of a singular favorable situation.

Correct answer: with

Explanation: The preposition 'with' is appropriate here as it indicates association, fitting grammatically and contextually with the phrase 'associated with low humidity.'

Meaning: 'With' indicates a connection or relationship between two things, in this case, the cold months and low humidity.

Wrong options:

• for: 'For' suggests purpose or benefit, which does not fit the context of association.
• on: 'On' is typically used to indicate a surface or a specific day, which does not convey the intended meaning of association.
• to: 'To' implies direction or destination, which is not suitable in this context.

Correct answer: average

Explanation: The word 'average' fits grammatically as it describes a typical number of infections, aligning well with the context of discussing common occurrences.

Meaning: 'Average' refers to the typical or mean amount, indicating how many infections an adult generally experiences in a year.

Wrong options:

• different: 'Different' suggests a contrast, which does not fit the context of describing a typical number of infections.
• ordinary: 'Ordinary' implies something common but does not specifically quantify the number of infections as 'average' does.
• same: 'Same' indicates identity, which does not convey the intended meaning of a typical frequency of infections.

Correct answer: keep

Explanation: The verb 'keep' fits grammatically as it suggests maintaining a distance, which is the intended action in this context. It aligns well with the imperative form used in the sentence.

Meaning: 'Keep' means to maintain or continue a certain state, in this case, maintaining distance from someone who is sick.

Wrong options:

• cover: 'Cover' does not fit the context of maintaining distance; it suggests protection or concealment instead.
• judge: 'Judge' implies forming an opinion, which is unrelated to the action of maintaining distance from a sick person.
• remember: 'Remember' suggests recalling information, which does not align with the action of keeping distance.