What physical features probably acted as barriers to settlements in the United States and Canada?

24-karat gold is considered to be pure gold. 18-karat gold is considered to be about 75% gold. what is 18-karat gold considered a mixture rather than a pure substance? a) it has a variable composition of other elements and minerals. b) its color is different than pure gold. c) the gold atoms are not arranged in a repeating pattern. d) it can be melted and transformed into a different substance.

Below is a description of a resource that you're considering using for a research paper. as you read the description, keep in mind what you've learned about historical thinking skills and use those skills in evaluating whether or not to use the source.

Which of the following best summarizes the idea represented by this graph?