Please help me answer the question

fourth option

Step-by-step explanation:

Common difference is given by difference of two consecutive term

d = nth term - (n-1)th term

for all the  series lets take second term as nth term

and first term as (n-1)th term

for first series

n th term = -3 1/2 = -3.5

(n-1)th term = -5

therefore

d= -3.5 -(-5) = -3.5 +5 = 1.5

for second series

n th term = 4 1/2 = 4.5

(n-1)th term = 2 1/2 = 2.5

therefore

d= 4.5 -(2.5) =2

for third series

n th term = 3

(n-1)th term =1.5

therefore

d= 3 - 1.5 = 1.5

for fourth series

n th term = -1.5

(n-1)th term = -4

therefore

d= -1.5 -(-4) = -1.5 + 4 = 2.5 = 2 1/2

Thus, based on above solution option four has common difference of 2 1/2