C.
<span>American troops finally withdrew.</span>
The correct answer is A. Nixon resigned before he could be impeached.
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Nixon resigned to try and protect some the decent reputation he had left.
If only one company provides a service it can monopolize that sector and cause price gouging. If several companies provide a service and those companies must be competitive with each other to attract business/customers.
The answer is A because Canada shows the most valuable amount of oil that produces.
He was criticizing their teachings and practices.