A system administrator needs to find all lines within '/var/log/syslog' that contain either 'error' or 'failed'. The administrator decides to use a command that supports regular expressions to accomplish this task. Which command will correctly output the desired lines?
egrep "error&&failed" /var/log/syslog
egrep "error|failed" /var/log/syslog
egrep "'error'|'failed'" /var/log/syslog
egrep "/error|failed/" /var/log/syslog