对下述复试系统的需求描述进行建模，设计UML图，并用UML绘图工具绘制UML类图。
提交压缩包至微课堂系统（http://10.69.42.177），包括：
1) jpg或其它图片格式的. UML类图
2) 相关分析过程的excel或word文档
Retest System
The retest system is used to automatically generate a set of test papers for each student. The system maintains a test database, which contains three types of questions, mathematics questions, English questions and professional topics. Each question has a unique identification code, question stem, difficulty coefficient and scoring standard. The score of each question is 10 and can be repeatedly extracted. besides:
Mathematical problems also include picture address, used to display formulas or graphics, calculation instructions;
English questions also include the types of questions (e.g. E-C, C-E, listening);
Professional topics also include program description, program body, image address for display and operation demonstration.
The system also maintains a student directory. Each student has a unique identification code in addition to the name. The system can randomly generate a full score of 100 retest papers for each student, including 3 English questions, 3 mathematics questions, and 4 professional courses. Each test paper contains 10 items to record the score of each test question.
In the retest system, users can:
Add students to the system;
Display all students;
Display exam paper through student identification code (including test question number, question stem and difficulty coefficient)；
Generate random retest papers for designated students;
Enter the retest score of the designated student;
View the total score of the re examination for the specified students.
Check the score of each question in the retest of the designated student.
这是答案吗