Jackson is building a website for his shoe repair shop and wants to use "soleservices.com" as his domain name. Which of the following would be helpful for Jackson to do in order to make sure "soleservices.com" is available?

a$.$

Contact an attorney specializing in domain registration to file the domain name with appropriate government agencies.

b$.$

Apply for the domain name with the U$.$S$.$ patent office.

c$.$

Contact other shoe repair websites to ensure they approve the domain name.

d$.$

Use a domain lookup tool to make sure the domain name isn't already taken.