These works are novels by R.K. Narayan.
Their chronological order is important.
The English Teacher was published first.
After that came:
\[
\textit{Mr. Sampath}.
\]
Then:
\[
\textit{The Financial Expert}.
\]
Finally:
\[
\textit{Waiting for the Mahatma}
\]
was published later.
Therefore, the correct chronological order is:
\[
\textit{The English Teacher} \rightarrow \textit{Mr. Sampath} \rightarrow \textit{The Financial Expert} \rightarrow \textit{Waiting for the Mahatma}.
\]
So the correct sequence is:
\[
A,\ C,\ B,\ D.
\]