11.   One works by crossing two parents with slightly different genetic codes, and mixing their genes randomly.

12.   The monoclonal antibodies work by combating the T-Lymphocytes and other threatening cells.

13.   The orchestra will be at the Festival Hall tonight, performing a selection of works by Russian composers.

14.   The sugar program works by limiting domestic production and erecting trade barriers that keep the price of imported sugar high.

15.   The windows in the roof gave us a good light to work by.