The correct keyword for restricting the records that are returned from a SELECT query based on a supplied criteria for the values in the records is WHERE. The WHERE clause is used to filter records based on one or more conditions. The syntax of the WHERE clause is:
SELECT column1, column2, ... FROM table_name WHERE condition;
The condition can be a logical expression that evaluates to true, false, or unknown. The condition can also use comparison operators, logical operators, and wildcards to specify the criteria. For example, the following query selects all the records from the employees table where the salary is greater than 50000:
SELECT * FROM employees WHERE salary > 50000;
The other options are incorrect because they have different purposes in SQL:
LIMIT is used to specify the maximum number of records to return from a query. For example, the following query returns only the first 10 records from the employees table:
SELECT * FROM employees LIMIT 10;
FROM is used to specify the table or tables from which to retrieve data. For example, the following query selects all the columns from the employees table:
SELECT * FROM employees;
IF is used to execute a block of code conditionally. For example, the following query updates the salary of an employee based on their performance:
UPDATE employees SET salary = IF(performance = 'excellent', salary * 1.1, salary) WHERE employee_id = 123; Reference:
https://bing.com/search?q=SQL+statements+restrict+records+based+on+criteria
https://stackoverflow.com/questions/11611931/sql-query-to-select-records-based-on-criteria

/etc/hosts.allow
Explanation:
The /etc/hosts.allow file contains a set of rules that specify which services and hosts are allowed to connect to the server by going through a TCP Wrapper program such as tcpd. TCP Wrappers are a security mechanism that can filter incoming requests based on the source address, destination address, and service name. TCP Wrappers can also perform logging, redirection, and execution of commands based on the rules.
The /etc/hosts.allow file has the following format:
service_list : host_list [ : option_list ]
The service_list is a comma-separated list of service names, such as sshd, telnet, or ftp. The host_list is a comma-separated list of host names, IP addresses, or network masks that are allowed to access the services.
The option_list is an optional list of keywords that can modify the behavior of the rule, such as twist, spawn, deny, or allow.
For example, the following rule in /etc/hosts.allow allows ssh access from any host in the 192.168.1.0/24 network, and logs the connection attempt:
sshd : 192.168.1.0/255.255.255.0 : spawn /bin/echo %a from %h attempted to access %d >> /var/log/sshd.log The /etc/hosts.allow file is processed before the /etc/hosts.deny file, which contains the rules for denying access to the server. If a request matches a rule in /etc/hosts.allow, it is granted access and the processing stops. If it does not match any rule in /etc/hosts.allow, it is checked against the rules in /etc/hosts.deny. If it matches a rule in /etc/hosts.deny, it is denied access and the processing stops. If it does not match any rule in either file, it is granted access by default.
References:
* LPI 102-500 Exam Objectives, Topic 110.3: Implement host security
* LPI 102-500 Study Guide, Chapter 10: Securing Your System, Section 10.3: TCP Wrappers
* hosts.allow man page

/etc/cron.allow
Explanation:
The /etc/cron.allow file is a file that contains a list of users who are allowed to use the cron scheduling system.
The cron scheduling system is a way of running commands or scripts at specified times or intervals. Users can create their own cron jobs by using the crontab command, which edits a file called crontab that stores the user's scheduled tasks. However, not all usersmay have access to the crontab command or the cron system.
The access is controlled by two files: /etc/cron.allow and /etc/cron.deny. If the /etc/cron.allow file exists, then only the users listed in this file can use the crontab command and the cron system. The file should have one user name per line. If the /etc/cron.allow file does not exist, then the /etc/cron.deny file is checked. If this file exists, then the users listed in this file are denied access to the crontab command and the cron system. If neither file exists, then the access depends on the configuration of the cron daemon, which is the program that runs the cron jobs. By default, only the root user can use the cron system if no files exist. The root user can always use the cron system regardless of the existence or content of these files. To create or edit the
/etc/cron.allow file, the root user needs to use a text editor such as vi, nano, or emacs. For example, to allow the users alice and bob to use the cron system, the root user can use the following command:
sudo vi /etc/cron.allow
And then add the following lines to the file:
alice bob
And then save and exit the file. References:
* How cron.allow and cron.deny can be used to limit access to crontab for ...
* /etc/cron.allow - Linux Bash Shell Scripting Tutorial Wiki
* Linux / UNIX Restrict at / cron Usage To Authorized Users