A： much too, stressed
B： too much, more stressed
C： too many , less stressed
D： a lot, less stressed
一个单峰函数y=f（x）的因素x的取值范围是20，30，用黄金分割法安排试点，x1，x2，x3，x4 …中，若x1＜x2，x1，x3依次是好点，则x4=____ ．
Hello, I'm Helen. I'm twelve years old. I'm in Garden Primary School. Jane is my classmate. We're good friends. I've got a green bicycle. It's new. I often ride the bicycle to go out and play. Today is Sunday. Jane and I go to visit Aunt Wang by bicycle. She lives in Pudong. She works in a hospital. She likes to make sick people better. She works very hard. It's 5: 45 now. It's dark outside. We must say goodbye to Aunt Wang.
下列遗传病中，由染色体变异引起的是（ ）
