Your ISP $($Internet Service Providers$)$ gives you an IP address, and it's public knowledge which ISPs have access to which IP addresses, thus:

a$.$ geotargeting is illegal due to privacy concerns.

b$.$ IP addresses can be used in geotargeting.

c$.$ IP addresses are primarily used for identifying device manufacturers.

d$.$ geotargeting cannot be used to serve advertising $.$

e$.$ GPS is based on IP addresses