The correct answer is A. UNION ALL.

UNION ALL is a SQL statement that appends two tables that have the same number of columns and compatible data types.UNION ALL preserves all the rows from both tables, including any duplicates12

B. MERGE is not correct, because MERGE is a SQL statement that combines the data of two tables based on a common column.MERGE can perform insert, update, or delete operations on the target table depending on the matching or non-matching rows from the source table34

C. GROUP BY is not correct, because GROUP BY is a SQL clause that groups the rows of a table based on one or more columns.GROUP BY is often used with aggregate functions, such as SUM, AVG, COUNT, etc., to calculate summary statistics for each group56

D. JOIN is not correct, because JOIN is a SQL clause that combines the data of two tables based on a common column or condition. JOIN can produce different results depending on the type of join, such as INNER JOIN, LEFT JOIN, RIGHT JOIN, etc.