Slate is much more commonly found in wet areas, especially around rivers in the United States, so it wouldn't be very available to Natives who were more inland.
Anvil is a tool used by blacksmiths, and it is the surface on which the object is placed which is worked on with a hammer- stroked with a hammer.
von Bülow meant (in 1899) that Germany will either have to colonize others ( be the hammer) or it would have to risk being colonized itself (being the anvil), hence showing the need for Germany to participate in colonization.
The correct answer is A. The man who assassinated Kennedy.
Explanation
John F. Kennedy (1917-1963) was the president of the United States from 1961 to 1963 when he was killed in the city of Dallas in the state of Texas by Lee Harvey Oswald, who days later would also be killed by Jack Ruby in a confusing episode when he was being taken to an investigation before a judge. The reasons for Lee Harvey Oswald to assassinate the president are uncertain, but when he was killed a few days after the President's assassination there was no clarity about the fact beyond the insistent self-declaration as innocent of Harvey Oswald. So, the correct answer is A. The man who assassinated Kennedy.