根据动作对环境的依赖程度的不同，可以将运动技能划分为_________和_________
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空调充注制冷剂一般有充注液态制冷剂和（）。
A. 充注气态制冷剂
B. 充注气液混合制冷剂
C. 充注高压制冷剂
D. 充注低压制冷剂
大型工件划线时，合理地选用第一划线位置，是为了提高（）和简化（）。
炭和石墨材料属于多孔物质，衡量多孔物质的密度有两种测定方法：（）。
You created a view called EMP_DEPT_VU that contains three columns from the EMPLOYEES and DEPARTMENTS tables: EMPLOYEE_ID, EMPLOYEE_NAME AND DEPARTMENT_NAME. The DEPARTMENT_ID column of the EMPLOYEES table is the foreign key to the primary key DEPARTMENT_ID column of the DEPARTMENTS table. You want to modify the view by adding a fourth column, MANAGER_ID of NUMBER data type from the EMPLOYEES tables. How can you accomplish this task?（）
ALTER VIEW emp_dept_vu (ADD manager_id NUMBER);
B. MODIFY VIEW emp_dept_vu (ADD manager_id NUMBER);
C. ALTER VIEW emp_dept_vu AS SELECT employee_id, employee_name, department_name, manager_id FROM employee e, departments d WHERE e.department_id = d.department_id;
D. MODIFY VIEW emp_dept_vu AS SELECT employee_id, employee_name, department_name, manager_id FROM employees e, departments d WHERE e.department_id = d.department_id;
E. CREATE OR REPLACE VIEW emp_dept_vu AS SELECT employee_id, employee_name, department_name, manager_id FROM employees e, departments d WHERE e.department_id = d.department_id;
F. You must remove the existing view first, and then run the CREATE VIEW command with a new column list to modify a view.
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