Refer to the exhibit. A network administrator is troubleshooting BGP configuration and wants to display only routes that originated in AS 40. Which regular expression should the administrator use in the command show bgp ipv4 unicast regex regex-pattern ?

In troubleshooting BGP, regular expressions (regex) can be used to parse through the large number of available ASNs. Regular expressions are based on query modifiers used to select the appropriate content. The regex pattern _40$ indicates to only include the lines that originated in AS 40 (the last AS in the AS-Path). Some regex query modifiers are as follows:
_ (underscore) – matches a space
^ (caret) – indicates the start of a string
$ (dollar sign) – indicates the end of a string
. (period) – matches a single character, including a space
* (asterisk) – matches zero or more characters or patterns