Assertion : $N, N$-Diethylethanamine is more basic than $N, N$-dimethylmethanamine. Reason : $+I$-effect of ethyl is more than methyl.

• Correct answer
  A

  If both assertion and reason are true and reason is the correct explanation of assertion.
• B

  If both assertion and reason are true but reason is not the correct explanation of assertion.
• C

  If assertion is true but reason is false.
• D

  If both assertion and reason are false.

Hence, the correct answer is option: 'A'.