The commands that can be used to display the local routing table are netstat and route. Both commands can show the kernel routing tables, which contain information about the network destinations and the gateways to reach them. The netstat command can be used with the -r option to display the routing table, and the -n option to show numeric addresses only. The route command can also be used with the -n option to display the routing table without resolving names. However, both netstat and route are considered obsolete and have been replaced by the ip route command, which is the current recommended way of printing the routing table in Linux12. Reference:
1: Understanding Routing Table - nixCraft
2: How To Display Routing Table In Linux - RootUsers
3: linux networking - What is the local routing table used for? - Server Fault

The command sequence uses a while loop to read the input from the echo command and assign the values to the variables a, b, and c. The read command reads one line of input at a time and splits it into words according to the IFS variable, which is a space by default. The first word is assigned to the first variable, the second word to the second variable, and so on. If there are more words than variables, the remaining words are assigned to the last variable. In this case, the input line has six words, so the read command assigns 1 to a, 2 to b, and 3 4 5
6 to c. Then, the echo command prints the result with the variables in reverse order, i.e., $c $b $a. Therefore, the output is result: 6 5 4 3 2 1. However, the answer choices only show the first three words of the output, so the correct answer is A. result: 6 5 4. References: [LPI 102-500 Exam Objectives], Topic 105.3: Customize and use the shell environment, Weight: 4. [LPI Linux Essentials Study Guide], Chapter 7: The Linux Operating System, Section 7.2: Shell Scripting.

logger
Explanation:
The logger command can be used to generate syslog entries of any facility and priority. It is a shell command interface to the syslog system log module. It allows users to write messages to the system log from the command line or from a script. The logger command supports several options to specify the facility, priority, tag, message, and other attributes of the log entry. For example, the following command generates a log entry with the facility user and the priority info:
logger -p user.info "This is a test message"
The facility and priority can be any of the values defined in the syslog protocol, such as kern, mail, auth, local0, etc. for the facility, and emerg, alert, crit, err, warn, notice, info, debug, etc. for the priority. The default facility is user and the default priority is notice. The logger command can also read messages from standard input or from a file. For more information, see the logger man page or the logger - Linux man page online. Reference:
Syslogs in Linux: Understanding Facilities and Levels
What are Syslog Facilities and Levels? - Trend Micro
syslog-ng Open Source Edition 3.30 - Administration Guide
Syslog Logging Guide: Advanced Concepts - CrowdStrike

The set command is used to display or modify the shell variables and functions in the current shell. When used without any arguments, it prints the names and values of all shell variables, including environment variables and user-defined variables, in alphabetical order. The output also includes the shell options and the positional parameters. The set command can be used in any POSIX-compliant shell, such as bash, zsh, ksh, etc123.
The other options are not correct because:
env is used to print or modify the environment variables, not the shell variables. It does not show the user-defined variables or the shell options. It can also be used to run a command in a modified environment45.
env -a is an invalid option for the env command. The -a option is not supported by the env command in any standard or common implementation45.
echo $ENV is used to print the value of the environment variable ENV, not the list of all shell variables. The ENV variable is usually set to the name of a file that contains commands or aliases to be executed by the shell. It is mainly used by the ksh and some versions of bash .