A part of sentence is bold. Below are given alternatives to the bold part at (A), (B) and (C) which may improve the sentence. Choose the correct alternatives. In case no improvement is needed your answer is (D).

Q:

The day he quits smoking, I shall celebrate.

• 1
  he quit
• 2
  he is quitting
• 3
  he had quit
• 4
  No improvement