（其中有杠杆原理和浮力理论的叙述，还有声学和光学的记载。）

根据短文理解，选择正确答案。

    My writing career began ten years ago with my articles published locally and nationally. As a beginning writer, I was happy to be on my way, writing and learning as much as I could . With two little kids underfoot, as well as working full-time, it was really difficult to make time for writing, but I managed.

    Readers told me they laughed, cried or were inspired by my articles. But they didn't know what was really going on behind the typewriter. I was not a happy mommy, and found it difficult to enjoy the everyday little things in life. In short, I was not a happy person.

    I realized I had to make some changes. I started walking every morning. It cleared my head, allowed me time to think, gave me fresh air, and made me feel invigorated (精神焕发） and healthy. I was eating wisely, and the weight started to go. I started a new job, joined a monthly writing chapter，and was determined to keep up my walking. Finding the balance was sometimes difficult. But I was determined to fit in writing time because it made me happy. Sure I loved to watch the news and have my tea, but that wasn't what made me truly happy.

    My own happiness has shown through my family, my job performance and my attitude towards challenging situations. I again have readers telling me the effect my writing has had on them, with some able to get on with their own writing because of my articles.

    It was up to me to make it happen—my own happiness. One step at a time-one word at a time. And I did it.