A protein is a large，complex macromolecule composed of one or more long chains of amino acids （氨基酸）.Present in and vital to every living cell，proteins are essential for the structure，function，and regulation of the body's tissues and organs.Yet，before Frederick Sanger-one of only two people to ever receive two Nobel Prizes in the same category-little was known about proteins and the sequence （排序） of their amino acid chains.
   Frederick Sanger graduated with a doctorate in biochemistry from St.John's College in 1943.Yet，it wasn't until his work with insulin （胰島素 ） that Sanger differentiated himself in the field of chemistry.His first true accomplishment occurred when he successfully determined the complete amino acid sequence of two protein chains in bovine（ 牛） insulin in the early 1950s.His research proved that proteins have a defined chemical con #position，and he eventually concluded that every protein had a unique sequence.In 1958，Sanger was awarded the Nobel Prize in Chemistry for showing how amino acids link together to form insulin，and，therefore，providing the tools for scientists to analyze any protein in the body.
   He went on to think about the ideas of how DNA codes for proteins.Together with another scientist，Sanger published the "Plus and Minus 7 technique，" a sequencing procedure to determine the order of the chemical bases which spell out the genetic code for all living things.When he designed a more efficient method in 1977，he named it the "Sanger Method".The "Sanger Method "allows long stretches of DNA to be rapidly and accurately sequenced，which earned him his second Nobel Prize in Chemistry in 1980.
   This method eventually allowed scientists to decode the three billion letters of the human genetic code，giving science the ability to distinguish between normal and abnormal genes.In the same way，Sanger's work directly contribute to the development of biotechnology drugs like human growth hormone.

（1）Why does the passage starts with mentioning the function of proteins？

B

B

A.To lead in the topic of biochemistry.
B.To attract the attention of the readers.
C.To illustrate the significance of Sanger's discovery
D.To show the complexity of bodies' tissues and organs
（2）What mainly leads to Sanger's success？

A

A

A.His life-long commitment to the same scientific field
B.His choice of majoring in biochemistry in college.
C.His cooperative relationship with other scientists.
D.His courage of challenging former research findings
（3）What is the last paragraph mainly about？

C

C

A.Side effects of Sanger's findings.
B.Sanger's primary methods of research.
C.Practical applications of Sanger's discovery.
D.Proper justifications for Sanger's research process
（4）The author develops this article

A

A

A.in order of time.
B.in order of space.
C.by making comparisons.
D.by giving examples.