Arnold and Danny are two twin brothers that are celebrating their birthday. The product of their ages today is smaller by 9 from the product of their ages a year from today. What is their age today?
Choose the correct choice from the following:	A) 2 .	B) 4 .	C) 5 .	D) 7	E) 9 .

Rationale: "ad = ( a + 1 ) ( d + 1 ) - 9 0 = a + d - 8 a + d = 8 a = d ( as they are twin brothers ) a = d = 4 b is the answer"
Answer: B