Ashallow depth of field means that what part of the photo will be in focus?

Depth of field is a zone of acceptable focus before and after the point focused upon. This zone is not split down the middle. As a general rule, this zone extends from the point focused upon, 2/3 away from the camera and 1/3 back towards the camera. The length of the zone is a variable based the camera’s aperture setting. 

These traits are all equally important in recognizing the validity of artwork mainly due to an artists' consistent style and reputation which they have developed over a lengthy period of time. most famous paintings contain specific characteristics of the artist who created it. an appraiser would pay close attention to certain key elements within the painting, as well as an accuracy in measurement and color shade. blended textures and outlines are essential in recognizing an authentic piece from a copy. signature and imagery exist in epic proportions to balance out each trait as they coexist in harmony, depending on preference and style of each artist. no two original pieces are virtually identical, although it may be almost impossible to see discrepancy with the naked eye.

Generally spontaneous human combustion is something that still bewilders some, human combustion happens very rarely and doesn't affect the surrounding areas, so unless you want to set your self on fire, human combustion will remain spontaneous and very rare.