I think it's a because every word has a subject and a verb
The best answer is the first option:
<span>For seven nights, he sneaks into the old man’s room and watches the sleeping man.
A good way to select the right answer is to read all of the options out loud. Which combination of the sentences sounds the most fluid and logical when you read it, and best preserves the meaning of the sentence? The first option does this best. </span>
Answer:
Hitler's invasion of Poland in September 1939 drove Great Britain and France to declare war on Germany, marking the beginning of World War II.
