$A$ and $B$ each select one number at random from the distinct numbers $1, 2, 3, \ldots, n$. The probability that the number selected by $A$ is less than the number selected by $B$ is $\frac{1009}{2019}$. The probability that the number selected by $B$ is the number immediately next to the number selected by $A$ is:

• A
  $\frac{2018}{2019}$
• B
  $\frac{2018}{(2019)^2}$
• C
  $\frac{2000}{2019}$
• D
  $\frac{2000}{(2019)^2}$