[问答题] 简要叙述资产评估的贡献原则。

You need to modify the STUDENTS table to add a primary key on the STUDENT_ID column. The table is currently empty.Which statement accomplishes this task?（） [" ALTER TABLE students ADD PRIMARY KEY student_id;"," ALTER TABLE students ADD CONSTRAINT PRIMARY KEY (student _ id);"," ALTER TABLE students ADD CONSTRAINT stud _ id _pk PRIMARY KEY (student _ id);"," ALTER TABLE students MODIFY CONSTRAINT stud _ id _pk PRIMARY KEY (student _ id)"] 城市公共汽车运营方式有哪些？各自有何特点？ 一个数组中的各元素的数据类型必须相同。 张某，男性，21岁，左小腿被钝性暴力打击，形成闭合性损伤，其局部处理下列哪项是错误的（） ["局部制动","抬高患肢","血肿加压包扎","早期局部热敷","血肿若进行性增大，需切开止血"] （）、重病患者遭受家庭暴力的，应当给予特殊保护。 ["未成年人","老年人","残疾人","孕期和哺乳期的妇女"] 简要叙述资产评估的贡献原则。