I should forewarn you, the test tomorrow will be challenging. What is the meaning of the word forewarn as it is used in this sentence?

To look forward
To see in the distance
To caution afterward
To caution in advance

Explain the effect of the juxtaposition of the following lines that serve as a beginniing to the new section that begins on page nine: anguish. german soldiers-with their steel helmets and their deaths-head emblem. still, our first impressions of the germans were rather reassuring.