C#/SQL Pre-Screen Questions

I'm in the market for a couple C# contractors and I was asked by our vendor to put together some basic pre-screen questions. Pretty easy stuff but hopefully it helps filters out some of the riffraff.

1. A class from which you cannot inherit is what type of class?
   1. Sealed   (Correct)
   2. Private
   3. Virtual
   4. Protected
2. What is the wild card character in the SQL “like” statement?
   1. *
   2. %   (Correct)
   3. $ 
   4. # 
3. Which method is exposed by the IDisposable interface?
   1. Finalize
   2. Clear
   3. Remove
   4. Dispose   (Correct)
4. What is the top .NET class from which all classes are derived?
   1. System.Class
   2. System.Object   (Correct)
   3. System.String
   4. System.Type
5. Can you store multiple data types in a System.Array?
   1. Yes
   2. No   (Correct)
6. To select all rows from the left table even if there are no matches in the right table what type of join is used?
   1. Inner Join
   2. Right Join
   3. Left Join   (Correct)
   4. Middle Join
7. What operator do you use to test for a null value?
   1. ??   (Correct)
   2. $
   3. @
   4. ?

Questions 1 & 2 are direct copies from M. Siler's post.