Li Xiang, a junior 2 student, wishes he never got a mobile phone. Last week, he went to see a doctor because there was something wrong with his arms and fingers. The doctor told him that he had “mobile phone disease(疾病)”. Now, more and more teenagers are getting “mobile phone disease” __ 78__of using mobile phones.

Li Xiang got his mobile phone six months __79__. He __80__ messages to his friends with it all the time, even when going to bed. Li Xiang started to do badly in exams because he spent too much time __81__ mobile phone games. His mom felt very __82__ about him, but he didn’t stop playing with the mobile phone __83__ his arms got injured（受伤）.

Yang Ling, a doctor, says that if someone plays his mobile phone too __84__, like Li Xiang, he will get “mobile phone disease”. If teenagers find their arms or fingers hurt (疼痛), they should go to see a doctor as soon as __85__. Yang says teenagers should try to use their mobile phones less, especially at school.

常用的试验设计类型有简比法（）设计

A、对比法

B、随机区组

C、拉丁方

D、裂区试验