The most likely reason for the end of Viking exploration and colonization is "a lack of adequate funding."
This is because according to historical evidence, the Viking exploration ended following the defeat of King Harald against the English King Harold Godwinson in 1066.
This defeat could lead to many effects on their raiding activities, which including a lack of money or funds to continue the expansion and raiding.
Also, option B is not correct because Sweden is part of the Viking territories.
Option C is not correct because gaining new lands to the East would only encourage them more to conquer more lands.
Option D is not correct because the onset of the Ice age was billion years ago.
Hence, in this case, the correct answer is option A " a lack of adequate funding."
Before the agricultural revolution much of England's farmland was "common" land, since there was far less competition in terms of the land being used for crop cultivation.
