Concept: In knowledge organization, subjects may be formed in different ways such as fusion, distillation, clustering and agglomeration.
Step 1: Match Fusion.
Fusion means combining two subjects to form a new subject. Astrophysics is formed by combining astronomy and physics.
\[
A \rightarrow IV
\]
Step 2: Match Distillation.
Distillation means a special subject emerging from a broader discipline. Anesthesiology is a specialized subject within medical science.
\[
B \rightarrow II
\]
Step 3: Match Clustering.
Clustering refers to a subject grouped around a person, idea or theme. Gandhiana is a cluster of literature and materials related to Mahatma Gandhi.
\[
C \rightarrow I
\]
Step 4: Match Agglomeration.
Agglomeration means bringing together a group of related subjects. Natural Science is a broad agglomerated subject area.
\[
D \rightarrow III
\]
Therefore, the correct matching is:
\[
A-IV,\ B-II,\ C-I,\ D-III
\]