Meaning: 'Within' means inside a certain period or limit, in this case, a short time.

Wrong options:

• in: The word 'in' suggests a point in time rather than a duration, which does not fit the context of producing benefits over a period.
• likely: 'Likely' is an adjective that does not relate to time and does not fit grammatically in this context.
• with: 'With' is a preposition that indicates accompaniment, which does not convey the intended meaning of time here.
• well: 'Well' is an adverb that describes manner, not a time frame, making it unsuitable for this blank.
• for: 'For' is a preposition that indicates purpose or duration but does not fit the context of indicating a specific time frame.
• both: 'Both' is a conjunction that refers to two items, which does not relate to the timing of benefits.

Correct answer: well

Explanation: The word 'well' serves as an adverb that modifies the action of cheering yourself up, fitting grammatically and contextually as it indicates the manner in which the action is performed.

Meaning: 'Well' means in a good or satisfactory manner, indicating how you cheer yourself up.

Wrong options:

• in: 'In' is a preposition that does not modify the action and does not fit the context of describing how to cheer up.
• likely: 'Likely' is an adjective that does not describe the manner of the action and is therefore inappropriate here.
• with: 'With' is a preposition that does not convey the manner of cheering up and does not fit grammatically.
• for: 'For' is a preposition that indicates purpose, which does not apply to the action of cheering up in this context.
• both: 'Both' is a conjunction that refers to two items, which does not relate to the manner of cheering oneself up.

Correct answer: both

Explanation: The word 'both' serves as a conjunction that connects two subjects, fitting grammatically and contextually as it refers to the two people involved in the action of smiling.

Meaning: 'Both' refers to two people or things together, indicating that the action affects both individuals.

Wrong options:

• in: 'In' is a preposition that does not connect subjects and does not fit the context of referring to two people.
• likely: 'Likely' is an adjective that does not serve as a conjunction and does not fit the grammatical structure here.
• with: 'With' is a preposition that does not connect subjects and is not appropriate in this context.
• well: 'Well' is an adverb that does not connect two subjects and does not fit grammatically.
• for: 'For' is a preposition that does not connect subjects and does not apply to the context of affecting two people.

Correct answer: because

Explanation: The word 'because' serves as a conjunction that introduces a reason, fitting grammatically and contextually as it explains why facial expressions and moods are catching.

Meaning: 'Because' is used to introduce a reason or explanation for something.

Wrong options:

• in: 'In' is a preposition that does not introduce a reason and does not fit the context of explaining the phenomenon.
• likely: 'Likely' is an adjective that does not serve as a conjunction and does not fit the grammatical structure here.
• with: 'With' is a preposition that does not introduce a reason and is not appropriate in this context.
• well: 'Well' is an adverb that does not introduce a reason and does not fit grammatically.
• for: 'For' is a preposition that does not introduce a reason and does not apply to the context of explaining why emotions are catching.

Correct answer: likely

Explanation: The word 'likely' serves as an adjective that indicates probability, fitting grammatically and contextually as it describes the likelihood of suffering depressive feelings.

Meaning: 'Likely' means probable or expected to happen, indicating a high chance of experiencing depressive feelings.

Wrong options:

• in: 'In' is a preposition that does not convey probability and does not fit the context of likelihood.
• within: 'Within' is a preposition that indicates a time frame, which does not relate to the probability of suffering feelings.
• with: 'With' is a preposition that does not express probability and is not appropriate in this context.
• well: 'Well' is an adverb that does not convey likelihood and does not fit grammatically.
• for: 'For' is a preposition that does not express probability and does not apply to the context of likelihood.