A main query can have more than one subquery.
B. The subquery and main query can retrieve data from different tables.
C. Multiple columns or expression can be compared between the subquery and main query.
Answers that are supposed to be correct are ridiculous. Scalar subqueries do not have to fetch data from the same table as main query. It is NOT true that only one column can be compared between the subquery and main query - you can use subquery with EXISTS condition, and you can compare whatever you want with correlated subquery.
A main query can have more than one subquery. 2. The subquery and main query must retrieve data from the same table. 3. Only one column or expression can be compared between the subquery and main query.
