Write the next sentence in the following story.

How to use a sleep tracker
Download a sleep tracking app for your phone.
A simple search of your phone's app store will reveal dozens of sleep tracker options, some free and some for sale. Nearly all of them, however, rely on your phone's existing accelerometer, which detects movement.

pick from the following.
(a). For most, your cellphone's design will allow you to install sleep trackers in less than one month. Try using a sleep tracker app on your phone, or using a web search engine.;
(b). Sleep tracking apps allow you to choose how much sleep you want, but make sure to check the apple website before entering your device's number or the name of your device. Let your device know that you wish to check it periodically.;
(c). Basically, you open the app and keep your phone in your pocket when you go to bed. If you are moving little or not at all, the app records this as sleep.;
(d). Buying a sleep tracker can be expensive, but the quality and accuracy are worth the investment for the purposes of tracking your smartphone's current timeover. Plug the device into your computer using an ethernet cable or turn it off.;. The answer should be
(c).