Answer:
The word "protracted" means lasting longer than expected, or unusually long, so what protracted most clearly means based on the context of the excerpt is how the time period of celestial motion studies must have lasted unusually long.
The linking verb is 'because'
The words the author chooses to use in a passage can change the whole tone and feeling of the story in many different ways, or add depth and detail to the story.
<span>You should include all jobs and volunteer work by attaching another page.
</span>The best way to list my work experience is to <span>start with your earliest job, plus volunteer, an add the other chronologically, then attach a CV that would list the other jobs, as an attached page is permitted in order to make the application complete. Not attaching the other page is also permitted but would leave jobs and so it could have a negative impact on my application.</span>
