Meaning: 'Turn off' means to deactivate or stop the operation of something, in this case, the car engine.

Wrong options:

• to turn off: This option is incorrect because it uses the infinitive form 'to turn off' which is not suitable here as the structure requires the base form without 'to'.
• turning off: This gerund form does not fit grammatically as it suggests an ongoing action rather than the intended directive to drivers.
• turned off: This past participle form is inappropriate in this context as it implies a completed action rather than a command or suggestion.

Correct answer: On average

Explanation: The phrase 'On average' serves as a discourse marker that introduces a generalization about the waiting time, fitting well contextually to provide statistical information.

Meaning: 'On average' means typically or generally, indicating a common or typical situation regarding the waiting time for drivers.

Wrong options:

• For instance: This option is incorrect as it implies providing an example rather than summarizing a general trend or statistic.
• In addition: This phrase suggests adding information rather than presenting a general average, which does not fit the context here.
• Of course: This phrase implies something is obvious or well-known, which does not align with the statistical nature of the information being presented.

Correct answer: majority

Explanation: The term 'majority' refers to the greater part of a group, which is appropriate here as it indicates that most drivers were not convinced by the sign, fitting both grammatically and contextually.

Meaning: 'Majority' means more than half of a group, indicating that most drivers did not comply with the request to turn off their engines.

Wrong options:

• exception: This term refers to something that does not follow a rule or pattern, which contradicts the context of discussing the general behavior of drivers.
• minority: This option implies less than half, which is incorrect as the context indicates that most drivers were not convinced, not just a few.
• unity: This term refers to being united or together, which does not fit the context of discussing compliance among drivers.

Correct answer: Although

Explanation: The word 'Although' introduces a contrast, indicating that despite some research suggesting effectiveness, the sign did not achieve its intended outcome, fitting well grammatically and contextually.

Meaning: 'Although' is used to introduce a statement that contrasts with or seems to contradict the previous statement, highlighting the complexity of the situation.

Wrong options:

• Since: This option implies causation, which does not fit the context as it does not introduce a contrasting idea.
• Because: This word indicates a reason, which is not suitable here as the sentence requires a contrast rather than an explanation.
• Thus: This term suggests a conclusion or result, which does not align with the need for a contrasting statement in this context.

Correct answer: alone

Explanation: The word 'alone' indicates that signs by themselves can influence behavior, fitting grammatically and contextually as it emphasizes the isolation of the sign's effect without additional factors.

Meaning: 'Alone' means by itself or without anything else, suggesting that signs can change behavior independently.

Wrong options:

• lonely: This term refers to a feeling of sadness due to lack of companionship, which does not fit the context of discussing the effectiveness of signs.
• neither: This word is used to indicate not one nor the other, which does not apply here as the context is about the effectiveness of signs, not a comparison.
• either: This term suggests a choice between two options, which is irrelevant in this context where the focus is on the singular impact of signs.