单项选择题

A. mkvdev -dev useful_scripts -vadapter vhost0; loadopt -vdev vtopt0 
B. mkvdev -optical useful_scripts -vadapter vhost0; loadopt -vdev vtopt0 
C. mkvdev -fbo -vadapter vhost0; loadopt -disk useful_scripts -vtd vtopt0 
D. mkvdev -type fbo -vadapter vhost0; loadopt -fbo useful_scripts -vtd vtopt0