有规则游戏的最大特点是（） ["通过模仿和想象，创造性地反映现实生活","把学习的任务和游戏的形式结合起来","以刺激儿童各种感官、运动机能发展为主","以儿童自主、自发表现出的活动为特征"]
Click the Exhibit button. Given this code from Class B： 25. A a1 = new A（）； 26. A a2 = new A（）； 27. A a3 = new A（）； 28. System.out.println（A.getInstanceCount（））； What is the result？（） [" Compilation of class A fails."," Line 28 prints the value 3 to System.out."," Line 28 prints the value 1 to System.out."," Compilation fails because of an error on line 28."," A runtime error occurs when line 25 executes."]
以下不属于导致水泥砂浆防水层起砂缺陷的原因是（）。 ["砂浆搅拌时加水过量","使用的水泥强度等级过低","养护不当","基层清理不当"]
充装民用液化石油气的气瓶字样为（）。 ["液化气；","液化石油气；","液化混合气；"]
Examine the data in the EMPLOYEES table. EMPLOYEES EMP_NAME DEPT_ID MGR_ID JOB_ID SALARY EMPLOYEE_ID 101 Smith 20 120 SA_REP 4000 102 Martin 10 105 CLERK 2500 103 Chris 20 120 IT_ADMIN 4200 104 John 30 108 HR_CLERK 2500 105 Diana 30 108 IT_ADMIN 5000 106 Smith 40 110 AD.ASST 3000 108 Jennifer 30 110 HR_DIR 6500 110 Bob 40 EK_DIR 8000 120 Revi 20 110 SA_DIR 6500 On the EMPLOYEES table, EMPLOYEE_ID is the primary key. MGR_ID is the ID of managers and refers to the EMPLOYEE_ID. The JOB_ID column is a NOT NULL column. Evaluate this DELETE statement: DELETE employee_id, salary, job_id FROM employees WHERE dept_id = 90; Why does the DELETE statement fail when you execute it?（） [" There is no row with dept_id 90 in the EMPLOYEES table."," You cannot delete the JOB_ID column because it is a NOT NULL column."," You cannot specify column names in the DELETE clause of the DELETE statement."," You cannot delete the EMPLOYEE_ID column because it is the primary key of the table."]
电力系统中发生短路有什么后果？
