How many pairs (r, r+1) have one or more prime factors common, where r is an integer and 2 ≤ r ≤9 ?	Pick.
A) 0	B) 1	C) 2	D) 3	E) 4
r and r+1 are consecutive integers.   Two consecutive integers are co-prime, which means that they don't share ANY common factor but 1. For example 20 and 21 are consecutive integers, thus only common factor they share is 1.   0nswer: 0.
<result>A</result>
How many pairs (r, r+1) have one or more prime factors common, where r is an integer and 2 ≤ r ≤9 ?