Step 1:
Inflation refers to a continuous rise in the general price level.
Step 2:
When prices rise, the same amount of money buys fewer goods and services.
Thus, purchasing power decreases.
Step 3:
• Assertion is correct
• Reason is also correct
• Reason properly explains the assertion
Step 4:
Hence, the correct answer is:
\[
\boxed{\text{(1)}}
\]