Step 1:
According to Keynes, consumption increases with increase in income, but not in the same proportion.
Step 2:
As income rises, many wants become satisfied and people tend to save a larger portion of additional income.
Step 3:
• Assertion is correct
• Reason is also correct
• Reason correctly explains the assertion
Step 4:
Hence, the correct answer is:
\[
\boxed{\text{(1)}}
\]