The question is asking us to determine the number of rows in which 18 paintings and 4 photographs could be displayed, such that there should be the same number of each type of art in each row. First we have to find the GCF ( the Greatest Common Factor ) of 18 and 4. 18 = 2 * 3 * 3 and 4 = 2 * 2. The prime factors of 18 are 2 and 3 and the prime factor of 4 is 2. Therefore GCF ( 18, 4 ) = 2. There could be 2 rows, with 9 paintings and 2 photographs in each. Answer: A . 2 rows.