Meaning: 'Best' refers to the highest quality or most favorable option available.

Wrong options:

• than: The word 'than' is a conjunction used for comparisons, which does not fit in this context as it does not describe a quality of the action.
• as: The word 'as' is a conjunction or preposition that indicates a role or function, which does not appropriately describe the action in this context.
• they: The word 'they' is a pronoun that refers to people or things previously mentioned, which does not fit as it does not describe the action or quality.
• better: The word 'better' is a comparative adjective that suggests improvement but does not indicate the highest quality, making it unsuitable here.

Correct answer: up

Explanation: The phrase 'speed up' is a phrasal verb that means to increase the rate of progress. It fits grammatically and contextually as it describes the action of enhancing the learning process.

Meaning: 'Up' in this context is used to indicate an increase in speed or efficiency.

Wrong options:

• by: The word 'by' is a preposition that indicates the means or method, which does not fit as it does not convey the action of increasing speed.
• than: The word 'than' is a conjunction used for comparisons, which does not relate to the action of speeding up the learning process.
• as: The word 'as' is a conjunction or preposition that indicates a role or function, which does not convey the action of increasing speed.
• undergo: The word 'undergo' is a verb that means to experience or endure something, which does not fit the context of enhancing speed.

Correct answer: undergo

Explanation: The word 'undergo' is a verb that means to experience or endure a process. It fits grammatically as it is the action that people will take regarding the learning process, and it aligns with the context of discussing the challenges of learning a language.

Meaning: 'Undergo' means to go through or endure a process or change.

Wrong options:

• they: The word 'they' is a pronoun that refers to people or things previously mentioned, which does not fit as it does not describe an action.
• best: The word 'best' is an adjective that describes quality, which does not fit as it does not convey an action in this context.
• better: The word 'better' is a comparative adjective that suggests improvement but does not indicate an action, making it unsuitable here.
• up: The word 'up' is an adverb that indicates direction or increase, which does not convey the action of experiencing a process.

Correct answer: by

Explanation: The word 'by' is a preposition that indicates the means or method through which something is achieved. It fits grammatically as it introduces the method of capturing attention and aligns with the context of discussing how to engage the public.

Meaning: 'By' indicates the means or method used to achieve something.

Wrong options:

• than: The word 'than' is a conjunction used for comparisons, which does not fit as it does not indicate a method or means.
• as: The word 'as' is a conjunction or preposition that indicates a role or function, which does not appropriately describe the means of capturing attention.
• they: The word 'they' is a pronoun that refers to people or things previously mentioned, which does not fit as it does not describe a means or method.
• up: The word 'up' is an adverb that indicates direction or increase, which does not convey the means of capturing attention.