Meaning: 'Conducted' means to carry out or perform an activity, in this case, an experiment.

Wrong options:

• dangle: The verb 'dangle' means to hang loosely, which does not relate to the action of performing an experiment.
• tramp: The verb 'tramp' means to walk heavily or noisily, which is irrelevant in the context of conducting research.
• abruptly: The adverb 'abruptly' describes a sudden action, but it does not fit as a verb to describe the researchers' actions.
• sustained: The verb 'sustained' means to maintain or support, which does not apply to the action of conducting an experiment.

Correct answer: cruise

Explanation: The verb 'cruise' fits contextually as it describes the action of driving at a constant speed, which is what the drivers were instructed to do. It maintains grammatical consistency with the infinitive form following 'to.'

Meaning: 'Cruise' means to travel smoothly at a steady speed, particularly in a vehicle.

Wrong options:

• dangle: The verb 'dangle' does not relate to driving and implies hanging, which is not applicable here.
• tramp: The verb 'tramp' refers to walking heavily, which does not fit the context of driving vehicles.
• abruptly: The adverb 'abruptly' indicates a sudden change, which contradicts the idea of maintaining a constant speed.
• sustained: The verb 'sustained' does not fit as it implies maintaining something rather than the action of driving.

Correct answer: smoothly

Explanation: The adverb 'smoothly' describes how the traffic moves, indicating that it is flowing without interruptions. This fits grammatically as it modifies the verb 'moves' appropriately.

Meaning: 'Smoothly' means in a steady and even manner, without bumps or interruptions.

Wrong options:

• dangle: The verb 'dangle' does not fit as it does not describe the manner of movement.
• tramp: The verb 'tramp' is unrelated to the context of traffic movement and implies heavy walking.
• abruptly: The adverb 'abruptly' suggests a sudden change, which contradicts the idea of smooth movement.
• sustained: The verb 'sustained' does not apply as it does not describe the manner of movement.

Correct answer: spread

Explanation: The verb 'spread' is appropriate here as it describes how the traffic jams extend backwards. It fits grammatically and contextually, indicating the action of the jams moving in a specific direction.

Meaning: 'Spread' means to extend over a larger area or to move outwards.

Wrong options:

• dangle: The verb 'dangle' does not relate to the movement of traffic jams and implies hanging, which is not applicable.
• tramp: The verb 'tramp' refers to walking heavily, which does not fit the context of traffic movement.
• abruptly: The adverb 'abruptly' suggests a sudden action, which does not describe the gradual nature of how jams spread.
• sustained: The verb 'sustained' does not apply as it implies maintaining rather than the action of spreading.