判断题

紫外可见光度法适用于不饱和有机化合物，尤其是共轭体系的鉴定，以此推断未知物的骨架结构。

【参考答案】

正确

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单项选择题

成语'饮鸩止渴”中第二个字的正确读音是()

A.jīu
B.jìu
C.zhèn
D.zhèng

单项选择题

Examine the data in the EMPLOYEES tablE.EMPLOYEESEMP_NAME DEPT_ID MGR_ID JOB_ID SALARYEMPLOYEE_ID101 Smith 20 120 SA_REP 4000102 Martin 10 105 CLERK 2500103 Chris 20 120 IT_ADMIN 4200104 John 30 108 HR_CLERK 2500105 Diana 30 108 IT_ADMIN 5000106 Smith 40 110 AD.ASST 3000108 Jennifer 30 110 HR_DIR 6500110 Bob 40 EK_DIR 8000120 Revi 20 110 SA_DIR 6500On 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_idFROM employeesWHERE dept_id = 90;Why does the DELETE statement fail when you execute it?（）A.There is no row with dept_id 90 in the EMPLOYEES tablE.B.You cannot delete the JOB_ID column because it is a NOT NULL column.C.You cannot specify column names in the DELETE clause of the DELETE statement.D.You cannot delete the EMPLOYEE_ID column because it is the primary key of the tablE.

A.EMPLOYEESEMP_NAME
B.ASST
C.Evaluate
D.
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F.

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