With the exception of the last sentence, all sentences are fluidly written and clearly connected between each other. In the case of the last example, the lack of transitional phrases between the two sentences creates a disconnection between the concepts expressed. While we might still be able to understand these sentences, we need to make the transition happen for ourselves as it was not included in the example.
Therefore, your best answer is option D.
1b) The Níger river is important because it helped the grow their crops and control trade on the river.
Cortez is the leader of the Aztecs and Pizzaro is the leader of a Spanish Conquistador who led an expedition that conquered the Inca Empire.
The correct answer is "landing a man on the moon." Before the US landed on the moon, the Soviet Union beat them in several different advances including having the first satellite to be launched into space. This satellite was known as Sputnik. However, the US was not willing to be second best to the Soviet Union
I think appeasement is not a good strategy with Hitler. He was too obsessed with a power which made Chamberlain's appeasement not a solution to stop his military aggression. If Chamberlain did not enter this diplomatic relation he could have defeated Hitler earlier.