If \(a\) and \(b\) are both single-digit positive integers, is \(a + b\) a multiple of \(3?\)
(1) The two-digit number \(ab\) (where \(a\) is in the tens place and \(b\) is in the one's place) is a multiple of \(3.\)
(2) \(a - 2b\) is a multiple of \(3.\)
Answer: D
Source: Manhattan GMAT