A、The main task of the physical layer is to ensure the correct transmission of the bit stream through the transmission medium
B、The transmission media connecting physical layer may have different types, such as optical fiber and wireless communication lines, etc.
C、Protocols of physical layer can be divide into two types: point-to-point communication lines and broadcast-based lines
D、Physical layer shields the difference between Ethernet and IP
喵查答案：Physical layer shields the difference between Ethernet and IP
Among the following descriptions of the physical layer, which is wrong?
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Generally speaking, the higher the sound quality is required, the higher the quantization level and the lower the sampling frequency is. -
The higher the sampling frequency, the closer the discrete digitized sound wave is to its original waveform. -
Audio files in WAV format do not use compression algorithm, so they have good sound restorability, strong stereoscopic impression and relatively large file capacity. -
MPEG video compression standards include MPEG-1, MPEG-2, MPEG-4, MPEG-7 and MPEG-21.
- 定义如下变量和数组： int k; int a[3][3]={1,2,3,4,5,6,7,8,9}; 则下面语句的输出结果是________。 for(k=0;k<3;k++) printf("%d ",a[k][2-k]);
- 下面程序的运行结果是________int main(){ int a[6],i; for(i=1;i3))%5; printf(“%2d”,a[i]); } return 0;}
- 定义如下的变量和数组int i;int y[2][3]={2,4,6,8,10,12}则下面语句输出结果for(i=0;i<2;i++)printf("%d ",y[1-i][i+1]);
- 以下程序段给数组所有的元素的输入数据，请选择正确的答案#includemain(){float x[5],m=0;while(m<5)scanf(“%.2f”,______);}
- 要求下面的程序运行后，显示如下结果：2 10 4 61 5 2 32 4 7 85 1 3 2则程序中的划线处应填入________.#include void main( ){ int a[4][4]={ ________ }; int i,j; for(i=0;i<4;i++) {for(j=0;j<4;j++) printf("%4d",a[i][j]); printf("\n"); }
- 执行下面的程序段后,变量a中的值为int a=3, s[5]={1};s[0]=a; a=s[2]*10;
- 执行下面的程序段后,变量a中的值为int a=3, s[5]={1,2};s[0]=a; a=s[2]*10;
- 下列程序执行后的输出结果是int a[3][3]={1,2,3,4,5,6,7,8,9};printf(“%d \n”,a[1][2]);