Concept:
In reported speech, when the reporting verb is in the past tense ("told"), the verb in the reported clause is generally shifted one step back in tense.
Step 1: Identify the reporting verb.
\[
\text{He told me}
\]
is in the past tense.
Step 2: Apply sequence of tenses.
The action of attending the meeting occurred before the telling.
Hence, past perfect tense is required:
\[
\text{had attended}
\]
Step 3: Choose the correct option.
\[
\text{He told me that he had attended the meeting.}
\]
\[
\boxed{\text{had}}
\]