Which of the following is a valid sql statement? a. c. customer#, order#, orderdate, shipdate from customers c natural join orders c; b. * from customers join orders on (customer#); c. c. customer#, order#, orderdate, shipdate from customers c, orders c where c. customer# = o. customer#; d. both b and c

Options A and C are valid SQL statements as JOIN is a JOIN clause that generate an implicit join based on the common columns in both tables.  

a. c.customer#, order#, orderdate, shipdate FROM customers c NATURAL JOIN orders c;

c. c.customer#, order#, orderdate, shipdate FROM customers c, orders c WHERE c.customer# = o.customer#;

Explanation:

In option A, there is an explicit join created between source table(customers) and the target table(orders) thus displaying the required data field names.

Option B is a JOIN clause with an ON clause. However, end-user can use the ON clause will have to be used only when there is more than one common column in both the tables.

Option C is the standard SQL statement using the WHERE clause based on the condition. Both A and C will return the same query output.