Which two are true about dropping columns from a table?

Examine the structure of the CUSTOMERS table: (Choose two.)

CUSTNO is the PRIMARY KEY.
You must determine if any customers' details have been entered more than once using a different CUSTNO, by listing all duplicate names.
Which two methods can you use to get the required result?

The EMPLOYEES table contains columns EMP_ID of data type NUMBER and HIRE_DATE of data type DATE.
You want to display the date of the first Monday after the completion of six month since hiring.
The NLS_TERRITORY parameter is set to AMERICA in the session and, therefore, Sunday is the first day of the week.
Which query can be used?

Examine the description of the CUSTOMERS table:

You need to display last names and credit limits of all customers whose last name starts with A or B in lower or upper case, and whose credit limit is below 1000.
Examine this partial query:

Which two WHERE conditions give the required result?

View the Exhibit and examine the data in the PRODUCT_INFORMATION table.

Which two tasks would require subqueries? (Choose two.)