Directions: For this part, you are allowed thirty minutes to write all open letter to the major of the city based on the following situation: You should write at least 150 words, and base your composition on the outline given below: 1. 1.近年来,本市空气污染情况越来越严重 2.你认为造成空气污染的主要污染源在哪里?应该采取哪些措施? 3.呼吁所有市民积极行动起来,治理空气污染