阅读下面短文，掌握其大意，然后从21—40各题所给的四个选项（A、B、C和D）中，选出最佳选项，并在答题纸上将该选项标号涂黑。
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 0F 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 evry 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 26 and coming back home.I said I couldn’t stand it one minute longer. I 27 be in prison! My father answered my 28 with just two lines-two lines that will always sing in my 29 - two lines that completely changed my life :
Two men looked out from prison bars
One saw the mud ,the other saw the stars
I read those two lines 30 I was ashamed of myself. I made up my mind I would find out what was good in my present 31 ; I would look for the stars
I made friends with the natives,and their 32 amazed me. They gave me presents of their favorite artworks which they had 33 to sell to toueists . I studied the delightful forms of the cactus .I watched for the desert sunsets,and 34 for seashells that had been left there millions of years ago when the desert had been an ocean 35
What brought about this 36 change in me ? The desert hadn’t changed , 37 I had .I had changed my 38 And by doing so ,I changed an unhappy experience into the most amazing 39 of my life . I was excited by this new world that I had dicovered I had looked out of my self-creatded prison and 40 the stars
38（）
A.attitude
B.principle
C.identity
D.standard