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?

To add a primary key to the STUDENT_ID column in the STUDENTS table, you would use the following SQL statement:

ALTER TABLE STUDENTS
ADD PRIMARY KEY (STUDENT_ID);

Here's the step by step explanation:

1. ALTER TABLE STUDENTS: This statement is used to add, delete/drop or modify columns in an existing table. It is also used to add and drop various constraints on an existing table. In this case, we're altering the table named 'STUDENTS'.

2. ADD PRIMARY KEY (STUDENT_ID): This is the action we're performing with the ALTER TABLE statement. We're adding a primary key to the table. A primary key is a field in a table which uniquely identifies each row/record in a database table. Primary keys must contain unique values. A primary key column cannot have NULL values. In this case, we're making 'STUDENT_ID' as the primary key.