A28-year-old female presents with severe chest pain and shortness of breath. she is diagnosed with pulmonary embolism, which most likely originated from the:

The pulmonary embolism is mostly likely to have originated from the Deep veins of the leg response feedback. Pulmonary embolism occurs when a clump of material, most often a blood clot, gets wedged into artery in your lungs. These blood clots most commonly come from the deep veins of your legs. It is a blockage of an artery in the lungs by a substance that has moved from else where in the body through the bloodstream. 

Its either a) or b),wind and water erosion gradually widen the canyon