Answer: option d. the Missouri and Ohio Rivers.
Explanation:
During the last ice age, there was reduction in the amount of solar radiation that hits the surface of the erth. As a result of this, some continents experienced a glacial growth and cold climates and the geography was also affected.
North America was covered by ice and the mid-western North America, the southern boundary of the north polar ice cap during past ice ages is marked by Missouri and Ohio Rivers.
To promote the growth of vegetation, Aborigines from Australia created grass fires to encourage new growth in vegetation and to allow the wild animals to eat the new plants resulting from the grass fire. They also used grass fires in order to roast some seeds that germinate only when burned. In return, these seeds provide them food.
Well since a hundred board should go by 10's until you reach 100, start at 61 then go up 10 spaces and the answer is 71
Hope this helps
~Jordan~
