7) B

nth term =   n
                 n + 1

So, (n + 1)th term:


    n + 1
 n + 1 + 1

n + 1
n + 2

Difference between (n + 1)th term and nth term:

n + 1  –     n
n +2      n + 1

n + 1 (n + 1)  –   n (n +2)
      (n + 2) (n + 1)

n² + 2n + 1 – n² – 2n
    (n + 2) (n + 1)

          1
 (n + 2) (n + 1)