John works as a Network Administrator for Perfect Solutions Inc. The company has a Linux- based network. John is working as a root user on the Linux operating system. He is currently working on his C

nice -n 19 sets the niceness to +19, which is actually the lowest CPU scheduling priority, the opposite of what is required.

nice without a -n argument uses a default niceness of +10, which lowers priority relative to the default; it does not grant the highest priority.

nice -n -20 sets the niceness to -20, which is the highest possible CPU scheduling priority in Linux. The & runs the compilation in the background, allowing John to continue other work. Because John is root, he is permitted to assign negative nice values, which are otherwise restricted for normal users.

nice cc -c *.c also uses the default niceness of +10 and additionally runs in the foreground, blocking the terminal without providing highest priority.