21£®--- Can you read the sign£¬sir? No smoking allowed in the lift!

---         £®

A£®Never mind                                       B£®Don’t mention it 

C£®Sure£®I don’t smoke                           D£®Pardon me

22£®—So I'm going to make the desk myself.

—Why____ instead, if I may ask?

      A£®not buy it          B£®don't buy one     C£®not buy one       D£®don't buy it

23£®—Oh, my God! I forgot his mobile phone number.

—What a pity 1 You___ it down on your notebook.

A£®could have written                               B£®should have written

C£®must have written                             D£®would have written