完形填空
When I was a teenager I volunteered to work at the water station at a 10,000m race. My job was to 1 water to the runners. I remember being so 2 to see all the different kinds of people who passed by and grabbed a cup of water. Some ran past, some walked past and a few wheeled past. I saw so many types of people doing it. I thought maybe I could do it too! So the next year I 3 up for the race.
That first 10,000m race was quite an4 I jogged, I walked, I jogged and I walked.5 I didn't know if I could finish. Then came a defining (决定性作用的)6.
At one point near the end, a 70-year-old man ran past me, very, very fast, and I felt7 because I was 15 years younger than he but I couldn't even keep up with him. I felt8for a second.
But then I 9something. He was running his race and I was running mine. He had 10 abilities, experience, training and goals for himself. I had mine. Remember my 11was only to finish.
After a minute, it 12 me that this was a lesson I could draw from. I learned something about myself in that moment. I turned my embarrassment into13.
I 14 that I would not give up on running races. In fact, I would run even more races and I would learn how to train and prepare 15and one day I would be one of those 70-year-old persons who were still running. As I crossed the finish line, I was proud of my16.
In life we all have those moments where we 17 ourselves to others. It's only 18. Don't allow those moments to 19 you. Turn them into motivation and let them inspire you. With the proper preparation and training, you can improve your result to 20anything you want in life.
（式中
是入射角，
是折射角，
、
分别为超声波在肝外和肝内的传播速度），超声波在肿瘤表面发生反射时遵循的规律与光的反射规律相同。已知
，入射点与出射点之间的距离是d，入射角为i，肿瘤的反射面恰好与肝脏表面平行，则肿瘤离肝脏表面的深度h为（ ）