To answer this question, we need to understand the SELECT clause in SQL.
The SELECT clause is used to specify the columns that you want to retrieve from a table in a SQL query. It determines which columns' data will be returned as the result of the query.
In a SELECT statement, you can specify any number of columns in the SELECT clause. There is no restriction on the number of columns you can include in the SELECT clause. You can select one column, two columns, three columns, or even more, depending on your needs.
Therefore, the correct answer is D) As many as needed.