Multi-choice problem: Continue writing the next sentence in this paragraph:

How to use pink noise for sleep
Play the sound of rain falling.
If you can find a recording online of rain falling, this can be a great source of pink noise. The sound of rainfall is one of the most soothing forms of pink noise available.

OPT: (A). It can be thought of as just a background noise, so it might not be affecting your sleep. Additionally, water from a hose, a breeze, or even the wind can disrupt your natural rhythm. (B). You can upload videos and use your phone, radio, mp3 player, desktop computer or other devices to create as many pink noise with the media as possible. If possible, make sure the effect is very minimal. (C). The sound of rainfall mimics a brook rushing down a river. Make sure the source of the rainfall is familiar, such as a particular river. (D). You may be able to find youtube videos that play the sound of rainfall for hours. You can also find tracks that play rainfall on a loop.
(D).