1. 若一个信道上传输的信号码元仅可取四种离散值,则该信道的数据传输率 S (比特率)与信号传输率 B (波特率)的关系是 ______ 。 %40font-face%20%7B%0A%20%26nbsp%3Bfont-family%3A%20%E5%AE%8B%E4%BD%93%3B%0A%7D%40font-face%20%7B%0A%20%26nbsp%3Bfont-family%3A%20%E5%AE%8B%E4%BD%93%3B%0A%7D%40font-face%20%7B%0A%20%26nbsp%3Bfont-family%3A%20%26quot%3B%40%E5%AE%8B%E4%BD%93%26quot%3B%3B%0A%7Dp.MsoNormal%2C%20li.MsoNormal%2C%20div.MsoNormal%20%7B%20margin%3A%200cm%200cm%200.0001pt%3B%20text-align%3A%20justify%3B%20font-size%3A%2010.5pt%3B%20font-family%3A%20%26quot%3BTimes%20New%20Roman%26quot%3B%2C%20%26quot%3Bserif%26quot%3B%3B%20%7D.MsoChpDefault%20%7B%20font-size%3A%2010pt%3B%20%7Ddiv.WordSection1%20%7B%20%7Dol%20%7B%20margin-bottom%3A%200cm%3B%20%7Dul%20%7B%20margin-bottom%3A%200cm%3B%20%7D A. S=B %40font-face%20%7B%0A%20%26nbsp%3Bfont-family%3A%20%E5%AE%8B%E4%BD%93%3B%0A%7D%40font-face%20%7B%0A%20%26nbsp%3Bfont-family%3A%20%E5%AE%8B%E4%BD%93%3B%0A%7D%40font-face%20%7B%0A%20%26nbsp%3Bfont-family%3A%20%26quot%3B%40%E5%AE%8B%E4%BD%93%26quot%3B%3B%0A%7Dp.MsoNormal%2C%20li.MsoNormal%2C%20div.MsoNormal%20%7B%20margin%3A%200cm%200cm%200.0001pt%3B%20text-align%3A%20justify%3B%20font-size%3A%2010.5pt%3B%20font-family%3A%20%26quot%3BTimes%20New%20Roman%26quot%3B%2C%20%26quot%3Bserif%26quot%3B%3B%20%7D.MsoChpDefault%20%7B%20font-size%3A%2010pt%3B%20%7Ddiv.WordSection1%20%7B%20%7D B. S=2B %40font-face%20%7B%0A%20%26nbsp%3Bfont-family%3A%20%E5%AE%8B%E4%BD%93%3B%0A%7D%40font-face%20%7B%0A%20%26nbsp%3Bfont-family%3A%20%E5%AE%8B%E4%BD%93%3B%0A%7D%40font-face%20%7B%0A%20%26nbsp%3Bfont-family%3A%20%26quot%3B%40%E5%AE%8B%E4%BD%93%26quot%3B%3B%0A%7Dp.MsoNormal%2C%20li.MsoNormal%2C%20div.MsoNormal%20%7B%20margin%3A%200cm%200cm%200.0001pt%3B%20text-align%3A%20justify%3B%20font-size%3A%2010.5pt%3B%20font-family%3A%20%26quot%3BTimes%20New%20Roman%26quot%3B%2C%20%26quot%3Bserif%26quot%3B%3B%20%7D.MsoChpDefault%20%7B%20font-size%3A%2010pt%3B%20%7Ddiv.WordSection1%20%7B%20%7D C. S=B/2 @font-face {  font-family: 宋体; }@font-face {  font-family: 宋体; }@font-face {  font-family: "@宋体"; }p.MsoNormal, li.MsoNormal, div.MsoNormal { margin: 0cm 0cm 0.0001pt; text-align: justify; font-size: 10.5pt; font-family: "Times New Roman", "serif"; }.MsoChpDefault { font-size: 10pt; }div.WordSection1 { } D. S=1/B @font-face {  font-family: 宋体; }@font-face {  font-family: 宋体; }@font-face {  font-family: "@宋体"; }p.MsoNormal, li.MsoNormal, div.MsoNormal { margin: 0cm 0cm 0.0001pt; text-align: justify; font-size: 10.5pt; font-family: "Times New Roman", "serif"; }.MsoChpDefault { font-size: 10pt; }div.WordSection1 { }