为了测定某组分的保留指数,气相色谱法一般采用的基准物质是( )。
A. 苯
B. 正庚烷
C. 正构烷烃
D. 正丁烷和丁二烯
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利用保留指数定性,正庚烷的保留指数值为___________.
Which protocol does the Internet mainly use? _____
A. The OSI reference model
B. TCP/IP
C. File Transfer Protocol
D. HTTP
An example ofclient-server application on the Internet would be _______
A. NIC
B. E-mail
C. Word
D. hard drive utilities
Which service dose the Internet not provide? ______
A. E-mail
B. WWW
C. ASP
D. FTP