**Concept: The question tests on the application of using equations to reach at a conclusion in a DS format**

**Solution:**

We are asked if a-1/b+1 = a/ b

Or we are asked if b (a-1) = a(b+1) [On cross multiplying]

Or if b a –b = a b + a

= > __If a = -b ?__

St (1) a= b-4

If b= 2 then a= 2-4 = -2 and hence a is EQUAL to –b (Yes)

However if b =4 a=0 and a is NOT EQUAL to –b (No )

Hence, two contradictory answers and thus St (1) is **Insufficient**

St (2) a = -b

It’s exactly what we are asking for in the question stem.

Thus **sufficient.** **Option (B)**

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