Answer:
nslookup
Step-by-step explanation:
Nslookup command is considered as one of the most popular command-line software for a Domain Name System probing. It is a network administration command-line tool that is available for the operating systems of many computer. It is mainly used for troubleshooting the DNS problems.
Thus, in the context, the technician receives the error "Web page cannot be displayed" when he alternates to access different web page, the nslookup command is the best command tool to find the root cause of the connection problem.