Concept:
Chronological order means arranging persons from earlier to later.
Step 1: Identify the earliest reformer.
Jyotiba Phule belongs to the earliest period among the given reformers.
So:
\[
D = \text{Phule}
\]
Step 2: Place Narayan Guru.
Narayan Guru came after Phule.
So:
\[
A = \text{Narayan Guru}
\]
Step 3: Place Periyar.
Periyar came after Narayan Guru.
So:
\[
B = \text{Periyar}
\]
Step 4: Place Ambedkar last.
Dr. B. R. Ambedkar belongs to the later period among these reformers.
So:
\[
C = \text{Ambedkar}
\]
Thus, the correct order is:
\[
D \rightarrow A \rightarrow B \rightarrow C
\]
Hence:
\[
\boxed{\text{(D) D, A, B, C}}
\]