At point x, only the air that is in direct contact with the sand is heated. and at point y, only subsurface sand that is in direct contact with the hot surface sand can gain heat. this means that mostly is occurring at points x and y.

Conduction

Explanation:

thrombocytopenia, which is a deficiency in blood platelets, can cause bleeding and bruising in the dermis similar to senile purpura. other possible causes include: exposure to ultraviolet rays and aging skin are common causes of senile purpura. senile purpura may also be a sign of collagen loss in the skin and bones.