5-1-8.若要将当前目录中的myfile.txt文件压缩成myfile.txt.tar.gz，则实现的命令为
A tar -cvf myfile.txt myfile.txt.tar.gz
B tar -zcvf myfile.txt myfile.txt.tar.gz
C tar -zcvf myfile.txt.tar.gz myfile.txt
D tar -cvf myfile.txt.tar.gz myfile.txt