Considering equal processing time for each segment, speed-up S achieved by a K-segment instruction pipeline operating on straight sequence of N instructions is given by:

Data:

number of instructions = N

number of stage (segment) = K

Non-pipeline

Assume each stage take 1 unit of time

Time taken (Twp)  = number of stage × number of instructions

Twp  = K.N 

For pipeline 

Only 1^st instruction takes K unit time then every (N - 1) instruction takes 1 unit time

Time taken(Tp) = (K + N - 1) 

\(S = \frac{T_{wp}}{T_{p}} = \frac{KN}{K+N-1}\)

Therefore option 4 is correct