Грамматика и Лексика

Преобразуйте, если это необходимо, слово NOT KNOW так, чтобы оно грамматически соответствовало содержанию текста.

It ____________ how these posts relate to the monument of Stonehenge. At this time, when much of the rest of southern England was largely covered by woodland, the chalk downland in the area of Stonehenge may have been an unusually open landscape.