In the web address www$.$microsoft.com, the $\backslash ".$com$\backslash "$ is the $\_\_\_\_\_\_\_\_$ meaning $\_\_\_\_\_\_\_\_.$

a$.$ pathname; location of the webpage

b$.$ top$-$level domain $($TLD$)$; commercial enterprise

c$.$ web server name; World Wide Web

d$.$ domain name; name of the organization