A.     Union selects only unique row (data) from all queries and Union all selects all rows from all queries.
     B.     Union selects row (data) from all queries and Union all selects all rows from all queries.
     C.     Union selects only unique row (data) from all queries and Union all selects rows from all queries.
     D.     Union selects row (data) from all queries and Union all selects rows from all queries.
   
 Ans: A