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)