Trade between the united states and canada has been problematic at times due to concern over a. canada's demand to reduce the amount of oil traded to the u. s. because of shortage in supply. b the contamination of canadian beef exports due to mad cow disease. c the contamination of american vegetables due to the overuse of pesticides. d the shortage of agricultural products that can be traded due to dry and flood conditions. my answer has asterisks (best answer gets brainliest)