If a and b are different positive integers and a + b+2 = a(a + b), then which of the following must be true?
I. a = 1
II. b = 1
III. a < b
Choose the correct choice from the following answers
A) I only
B) II only
C) III only
D) I and II
E) I and III
Number picking might not be the best way to solve MUST BE TRUE questions.   The question asks which of the followingMUSTbe true, or which of the following isALWAYStrue no matter what set of numbers you choose. For such kind of questionsif you can prove that a statement is NOT truefor one particular set of numbers, it will mean that this statement is not always true and hence not a correct answer.   So the set you chose just proves that II is not always true and hence it's not a part of a correct choice. As for I and III: they might be true for this particular set of numbers but not true for another set, so you can not say that I and III are always true just based on one set of numbers (it just happens to be that I and III are always true).   As forCOULD BE TRUEquestions:   The questions asking which of the followingCOULDbe true are different:if you can prove that a statement is truefor one particular set of numbers, it will mean that this statement could be true and hence is a correct answer.   II only
<result>B</result>
If a and b are different positive integers and a + b+2 = a(a + b), then which of the following must be true?
I. a = 1
II. b = 1
III. a < b