The Data Encryption Standard (   1   ) and the Advanced Encryption Standard (   2  ) are block cipher designs which have been designated cryptography standards by the US government (though DES's designation was finally withdrawn after the AES was adopted). Despite its deprecation as an officia1 standard, DES (especially its sti1l-approved and much more secure trip1e-DES variant) remains quite popu1ar it is used across a wide range of  applications，from ATM encryption to e-mail privacy and secure remote access .Many other block ciphers have been designed and re1eased, with considerable variation in qua1ity.Many have been thorough1y broken. See Category：（  3  ）.  
（  4  ）, in contrast to the ‘block’ type, create an arbitrari1y 1ong stream of  key materia1, which is combined with the p1aintext （ 5  ）or character-by-character,.somewhat  1ike the one-time pad. In a stream cipher, the output stream is created based on an interna1 state which changes as the cipher operates. That state change is controlled by the key, and, in some stream ciphers, by the p1aintext stream as well. RC4 is an examp1e of a well -known, and wide1y used, stream cipher; see Category：Stream ciphers. 
(1)A. DES  
B. AES  
C. RC4   
D. ATM   
(2)A. DES   
B.AES   
C. RC4  
D. ATM   
(3)A. Stream ciphers   
B. Sequence ciphers  
C. Symmetric ciphers  
D. Block ciphers   
(4)A. Stream ciphers   
B. Sequence ciphers  
C. Symmetric ciphers  
D. Block ciphers   
(5)A. word-by-word   
B. sentence-by-sentence  
C. bit-by-bit  
D. group-by-group