Washington D.C.'s metro train system is being extended further into the neighboring states of Maryland and Virginia, thereby reducing the cost of commuting into the United States' capital. Other things being held constant, this can be expected to:

A) increase the extent of the market for housing around Washington D.C.
B) have no effect on the extent of the market for housing around Washington D.C. as the actual geography remains unchanged.
C) have no effect on the extent of the market for housing around Washington D.C. as property taxes have not changed.
D) have no effect on the extent of the market for housing around Washington D.C. as the range of houses available has not changed.