California's biggest city, Los Angeles, has successfully reduced its smog problem. Its efforts included improving its vehicle emission standards, and offering special incentives or rewards for clean energy policies.加州最大的城市洛杉矶已经成功减轻了其烟雾问题.其措施包括提高车辆排放标准,为清洁能源政策提供额外奖励与回报.
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