Answer:
B. common cold and influenza
Social studies is always confusing. Get used to it.
The first sentence is referring to a secondary reinforce while
the second sentence is referring to primary reinforce. A primary reinforce are
usually base on biological things such as the water we drink or food that we
eat while the secondary reinforce is base on the conditions that humans is
reinforcing such as money or grades.
Answer: Relations between the Soviet Union and the United States were driven by a complex interplay of ideological, political, and economic factors, which led to shifts between cautious cooperation and often bitter superpower rivalry over the years. The distinct differences in the political systems of the two countries often prevented them from reaching a mutual understanding on key policy issues and even, as in the case of the Cuban missile crisis, brought them to the brink of war.
Explanation:
