执行高高原机场飞行任务的机长必须在所飞机型上的机长飞行经历时间满（）小时。

A.400小时

B.500小时

C.600小时

D.700小时

I live in the country and my father was a farmer.51. ______
He is now forty-five year old. Because of years of 52. ______
hard work, he looks old than his age. When I was53. ______
young, he is used to tell me the importance of study. 54. ______
Father knows little about English and other subjects, 55. ______
but he usually gives me some good advices on how56. ______
to learn my lessons good. He is not only kind to me 57. ______
but also very strict in me. With his help, I’ve made 58. ______
great progress. I’ll never to forget what he taught 59. ______
me. I think my father is best father in the world. 60. ______