Answer is:
E). They monitor email traffic.
Step-by-step explanation:
Track Your Device's IP Address with mail. If your laptop or smartphone was stolen, you can use a service like mail to find the IP address of your thief. When you log into those services from any computer, it logs the IP address used, and displays your last used IP in your account. So, these are source for finding the stolen laptop and smartphones.
I hope you got the idea. Thanks