Step 1: Simple Random Sampling.
Every unit has equal probability.
\[
a \rightarrow ii
\]
Step 2: Stratified Random Sampling.
Population divided into homogeneous strata.
\[
b \rightarrow i
\]
Step 3: Cluster Sampling.
Population divided into clusters.
\[
c \rightarrow iv
\]
Step 4: Systematic Sampling.
Every \(K^{th}\) unit selected.
\[
d \rightarrow iii
\]
\[
\boxed{a-ii,\ b-i,\ c-iv,\ d-iii}
\]
Hence,
\[
\boxed{\text{Option (B)}}
\]