― Tony, come down and help me with the heavy box!

― Come on! I ______ all day long. Get Peter to do that!

A. work                                                B. had been working     

C. had worked                                       D. have been working

______, Bell’s tetrahedron shape has proved invaluable in the design of bridges.

   A. To be stable                                     B. Being stable

   C. Stable                                             D. Having been stable

To invent something new, you should follow it up, ______ all around it and you will succeed in doing it finally.

   A. exploring             B. explored            C. having explored         D. explore

California, the third largest state in the USA, has the ______ of being the most multicultural state.

   A. distinction           B. drawback          C. division                    D. directory

______ television programs are an effective medium for advertising.

        A．Commercial           B. Conservative      C. Authentic                  D. Superior

______ having been told thousands of times to study hard, some students still overlook their teachers’ whole-hearted suggestions.

  A. Until                    B. Though             C. While                       D. Unless

With the development of cloning technology, some evil leaders hope to clone themselves to ______ their ambitions.

   A. acquire               B. obtain                C. attain                       D. accelerate

 It’s cold outside, but warming clothing will ______ the cold.

  A. keep back                    B. keep out           C.  keep up          D. keep from

---Do you know the “King of Pop” Michael Jackson died of heart disease?

--- Yes. But I thought he ______.

  A. might die of skin cancer                                   B. might have died of skin cancer

  C. should have died of skin cancer                         D. must die of skin cancer

Not until a search has been made to find out your product really is different from everyone else’s ______ a patent.

  A. you will receive                                        B. will you receive        

  C. do you receive                                         D. you received