Which of the following commands should be used to reset the Virtual Memory Manager tuning parameters to their default values？（）

A. renice -n -20 {PID}
B. renice -n 20 {PID}
C. renice -n -40 {PID}
D. renice -n 40 {PID}

A. Too many nfsd’s running
B. Client and server with different buffer sizes
C. Bridges， routers or gateways are receiving too many fragmentated packets
D. Too few nfsd’s running