The system hangs at boot time after starting NFS services. What is the most likely cause？（） 

A.The action parameter of rcnfs in /etc/inittab is ’off’ and the script called is not exiting.
B.The action parameter of rcnfs in /etc/inittab is ’wait’ and the script called is not exiting.
C.The action parameter of rcnfs in /etc/inittab is ’once’ and the script called is not exiting.
D.The action parameter of rcnfs in /etc/inittab is ’respawn’ and the script called is not exiting