Final answer:
The sit-down strike by the United Auto Workers resulted in their right to collectively bargain, leading to a long-term change in labor rights in the United States. Therefore, the correct option is A.
Step-by-step explanation:
The event described in option A is the sit-down strike launched by the United Auto Workers (UAW) union against General Motors. This strike resulted in the UAW's right to collectively bargain for all its members, marking a significant victory for organized labor.
The long-term change that resulted from this event was the establishment of collective bargaining rights for workers in the United States. It set a precedent for other unions to fight for the same rights and played a pivotal role in improving working conditions and increasing wages for millions of workers.