Why did the west rely on slavery

Gettysburg address question. what is the best line from the address? why do you think so?

Erika is a human resource manager at bluetel inc., a software company. she receives a call from an hr manager at another software company asking about marshall, a software engineer who used to work at bluetel and has applied for a job at the caller's company. erika checks the company's records and sees that a coworker had accused marshall of racial discrimination, but an investigation did not turn up any evidence to support the charge. marshall left the company two months later, saying he was no longer comfortable there. erika is concerned about sharing the details of this situation with the caller. if telling the information to the caller leads to the other company not hiring marshall, what potentially unlawful behavior could marshall accuse bluetel of engaging in?

What was one of the main goals of european exploration