This is a 15 minute study of a male torso drawn using a 3B pencil, paying close attention to details such as bone structure. I chose a vantage point where I could clearly see the whole of his chest without being sat directly in front of him, as I wanted to clearly be able to see the ribcage but sitting directly in front would make the drawing too two-dimensional. I used tonal values to give the form a more three-dimensional feel, however it still looks flat against the white background. Shading the background instead of leaving it white would stop it looking as flat, but I think that, in this instance, it isn't too much of an issue as there is nothing to distract from the detail inside the outline of the torso which is the main focal point.
Had this been a longer study than 15 minutes, I could have used a different shading approach to give the illustration a more realistic feel. I chose to shade very loosely instead to ensure the whole area was filled. I think this method also helps to draw attention to the skeletal structure under the skin as the low number of values exaggerates these slightly, making it seem more contrasty than highly realistic shading with more values would do.