This is a test of commonsense with single/multi-choices. Complete the next sentence:

How to track running distance
Download a fitness tracker app.
There are many different apps on the market for smartphone users to choose from. Some of the most popular include runkeeper, mapmyrun, and nike + running.

Choose from: (A). The app may also allow you to watch running distances in pictures. Use an app like this, to help conserve the battery of your smartphone.; (B). These apps typically come equipped with features like a stopwatch, step counter, and tools for averaging speed and pace. The majority of these apps are free for download.; (C). While virtual matches are not very available, running the app changes the equation by 25%, meaning that you won't even see a track on the screen if you're even running, so be careful. A tracking app will make the data stream feed up faster, decreasing your pace and increasing your distance.; (D). If you are not already signed in with your device, you will be asked to sign in with your personal account for this service. Tap " track distance " and sign in with your account details, then tap " miles " and your app will install, or use the app's time and area tools to look for a specific distance to track.;
The answer is:
(B).