Effects of Environmental Regulations on Domestic Production and Imports

Effects of Environmental Regulations on Domestic Production and Imports
-Refer to the figure above.The graph represents consumers and suppliers in country that relies on imports.Curve D is domestic demand, Curve S is domestic supply and Curve I is the import supply curve.The import supply curve is horizontal because

A) the world produces a relatively small amount of this good
B) no matter how much this country buys, their demand does not impact world price
C) this is a renewable good, for which there is no shortage
D) all of the above