Meaning: 'Opens' means to become accessible or available for use, indicating that the bridge was made available to the public after its construction.

Wrong options:

• closes: The verb 'closes' suggests the opposite action, indicating that something is no longer accessible, which contradicts the intended meaning of the sentence.
• appears: The verb 'appears' implies a visual presence rather than an action of becoming accessible, making it contextually inappropriate here.
• equals: The verb 'equals' suggests a comparison or equivalence, which does not fit the context of the bridge being made available to the public.

Correct answer: On

Explanation: The preposition 'On' is used to indicate a specific day or date, which is appropriate for referring to 'opening day.' This fits grammatically and contextually as it specifies the time of the event being discussed.

Meaning: 'On' is a preposition used to indicate a specific time or date, in this case, referring to the day the bridge opened to the public.

Wrong options:

• During: The preposition 'During' indicates a period of time rather than a specific point in time, making it unsuitable for this context.
• Since: The preposition 'Since' indicates a starting point in time and does not fit the context of referring to a specific day.
• When: The word 'When' is a conjunction that introduces a clause, but it does not function as a preposition to indicate a specific date.

Correct answer: marveled

Explanation: The verb 'marveled' is in the past tense and conveys a sense of wonder or admiration, which is appropriate for describing the reaction of the bridge walkers on opening day. This fits grammatically and contextually with the sentence structure.

Meaning: 'Marveled' means to have a feeling of great surprise or admiration, indicating that the bridge walkers were impressed by the bridge's grandeur.

Wrong options:

• stationed: The verb 'stationed' implies being placed in a specific location, which does not convey the intended sense of admiration or reaction to the bridge.
• looked: The verb 'looked' is too vague and does not capture the emotional response of admiration that 'marveled' conveys.
• laughed: The verb 'laughed' suggests amusement, which is not appropriate in the context of admiring a significant architectural achievement.

Correct answer: connects

Explanation: The verb 'connects' accurately describes the function of the bridge in linking two geographical areas, San Francisco and Marin County. This fits grammatically and contextually as it highlights the bridge's purpose.

Meaning: 'Connects' means to join or link together, indicating that the bridge serves to link San Francisco with Marin County.

Wrong options:

• separates: The verb 'separates' suggests division, which contradicts the function of the bridge as a link between two areas.
• channels: The verb 'channels' implies directing flow, which does not accurately describe the bridge's role in connecting land areas.
• differentiates: The verb 'differentiates' suggests distinguishing between two things, which does not fit the context of the bridge's purpose.

Correct answer: vehicular

Explanation: The adjective 'vehicular' describes traffic that consists of vehicles, which is appropriate in the context of the bridge being opened for use by cars and other vehicles. This fits grammatically and contextually with the sentence.

Meaning: 'Vehicular' refers to anything related to vehicles, indicating that the bridge was opened for vehicle traffic.

Wrong options:

• aquatic: The adjective 'aquatic' relates to water, which does not fit the context of traffic on a bridge.
• airborne: The adjective 'airborne' refers to things in the air, which is not relevant to the context of a bridge designed for vehicles.
• watertight: The adjective 'watertight' refers to something that does not allow water to pass through, which is unrelated to the context of traffic.

Correct answer: symbol

Explanation: The noun 'symbol' fits grammatically and contextually as it denotes something that represents or stands for something else, in this case, progress during a time of economic crisis. It aligns well with the overall sentiment of the sentence.

Meaning: 'Symbol' refers to an object or image that represents a larger idea or concept, indicating that the bridge represented progress in the Bay Area.

Wrong options:

• denial: The noun 'denial' suggests refusal or rejection, which does not fit the context of representing progress.
• technique: The noun 'technique' refers to a method or way of doing something, which does not convey the intended meaning of representation.
• yield: The noun 'yield' refers to the amount produced or the act of giving way, which does not align with the context of representing progress.