Concept:
Exchange rate movements affect the competitiveness of exports and imports.
Step 1: Analyze Statement (I).
When a country's currency depreciates, domestic goods become cheaper for foreign buyers.
As a result,
\[
\boxed{\text{Exports increase}}
\]
Hence Statement (I) is correct.
Step 2: Analyze Statement (II).
Depreciation makes imported goods more expensive.
Therefore imports generally decline.
\[
\boxed{\text{Statement (II) is incorrect}}
\]
Step 3: Analyze Statement (III).
Currency appreciation makes exports relatively expensive.
Thus exports generally decrease.
\[
\boxed{\text{Statement (III) is incorrect}}
\]
Step 4: Analyze Statement (IV).
Appreciation makes imports cheaper and therefore tends to improve imports.
\[
\boxed{\text{Statement (IV) is incorrect}}
\]
Hence only Statement (I) is correct.
\[
\boxed{\text{Option (D)}}
\]