What was the major cause of the Cold War? A. unprovoked aggression by the Soviet Union

B. the United States' policy of isolationism

C. different ideas about how to govern after World War II

D. poor leadership from Harry Truman and Joseph Stalin

A?

Explanation:

Hope this helps !!

-B

All the given elements belong to the second period of the periodic table

Explanation:

Let's locate the elements with the given atomic numbers:

Z = 3, this corresponds to lithium (Li);Z = 4, this corresponds to beryllium (Be);Z = 5, this corresponds to boron (B);Z = 6, this corresponds to carbon (C);Z = 7, this corresponds to nitrogen (N);Z = 8, this corresponds to oxygen, (O);Z = 9, this corresponds to fluorine, (F).

Now notice that each of these 9 elements can be found in the same row of the periodic table. This is period 2. We may then summarize that all of these elements belong to the same period, period number 2.