题目

During the war, my husband was stationed at an army camp in a desert in California. I went to live there in order to be  21   him. I hated the place. I had never  22  been so unhappy. My husband was ordered out on a long-term duty, and I was left in a tiny shack(棚屋) alone. The heat was         23  -almost 125 degrees even in the shade of a cactus(仙人掌).  24  a soul to talk to. The wind blew non-stop, and all the food I ate, and the very air I breathed,  were  25  with sand, sand, sand! I was so sorry for myself that I wrote to my parents. I told them I was用大小不同的力先后敲击同一个音叉，音叉两次发出的声音的_______（选填“音调”、“响度”或“音色”）不同，倒车雷达利用_____（选填“超声波”或“次声波”）探测障碍物，帮助司机倒车。