answer:
plasma membrane a microscopic membrane of lipids and proteins which forms the external boundary of the cytoplasm of a cell or in closes a vacuole, and regulates the passage of molecules in and out of the cytoplasm
answer number 2
the plasma membrane or cell membrane, is the phospholipid layer that surrounds the cell and protects it from outside environment.
you can use either answer if you have to type or write an answer 
 
        
             
        
        
        
RNA polymerase binds to the lac promoter and begins transcribing
the stretch of DNA to messenger RNA.
Therefore, in other words, the stretch of DNA is expressed. The DNA sequence of
the lac promoter 'signals' where the RNA
polymerase will bind and where transcription
will begin. Promoters are found upstream of a gene to be transcribed.