Choose the command to enable unique constraint sal_uni on salary column in Employees table. Employee Table: Eid EName Salary Join Date 1000 Q1 E11 Khalid E12 Asma E13 Ali E14 Zahra 500 600 10-10-2019 20-05-2018 25-06-2019 15-02-2019 1000 O a. ALTER TABLE EMPLOYEES ENABLE CONSTRAINT UNIQUE (salary); O b. ALTER TABLE EMPLOYEES ENABLE sal_uni: O C. ALTER TABLE EMPLOYEES ENABLE CONSTRAINT sal_uni; O d. ALTER TABLE EMPLOYEES DISABLE CONSTRAINT sal_uni: A table in which foreign key is defined is called Q2 O a. Master table O b. Detail table O c. Primary table O d. Default table Select the correct command to add Not Null constraint to column salary. Employee Table: Eid EName Salary Join Date Q3 1000 soo E11 E12 E 13 E14 Khalid Asma Ali Zahra 10-10-2019 20-05-2018 25-06-2019 15-02-2019 600 1000 a. Alter table Employee modify (salary constraint NN_sal NOT NULL): b. Alter table Employee modify (salary constraint NOT NULL): c. Alter table Employee add (salary constraint NN_sal NOT NULL O d. Alter table Employee acid constraint NN_sal NOT NULL(salary)