If (a-4)(b-2) =0, which of the following must be true ?
I. a=4 and b=2
II. if a is not = 4, then b=2
III. if a=4, then b is not=2
Choose the correct choice:
A) I only
B) II only
C) III only
D) I and II
E) II and III
(a-4)(b-2)=0   So either a=4 or b=2 or both. It is 'or' not 'and', so it could be any of the three possibilities. Thus I and III are not necessarily true.   The answer is II only.
<result>B</result>
If (a-4)(b-2) =0, which of the following must be true ?
I. a=4 and b=2
II. if a is not = 4, then b=2
III. if a=4, then b is not=2