Specify the following queries in SQL on the database schema of Figure

$2.$

$$

a

$)$

$$ Get the names of the courses that have two or more sections.

b

$)$

$$ Get the names of the instructors who are teaching at least two different courses in the same semester of the same year.

c

$)$

$$ Retrieve the names of students who took only one course in the Spring

$2020$

$$semester$.$