You cannot put any sort of endmark (period, question mark, or exclamation point) here because it is not a complete sentence. Complete sentences must have a subject and a predicate. You can tell there's not even a verb here, so this is just a fragment, and we would have to use a comma.
a. Very truly yours,
Christopher Columbus was an Italian-Roman explorer who found the Americas on his way to Europe in the 16th century, and his voyages led to centuries of transatlantic colonization.
The period between 1492 and 1504, during the period when Columbus was exploring the Atlantic Ocean by ship, he made several ocean-going trips by ship. These trips were during the time when he explored the Atlantic Ocean by ship. It was not possible for him to establish a straight water route from Europe to Asia, despite his determination. Instead, he was lucky enough to stumble upon the Americas. His explorations marked the beginning of centuries of exploration and colonization, despite the fact that he did not discover the New World, millions of people already lived there at the time.
<em>Hope this helps :)</em>
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<em>Hi there!</em>
<em>~</em>
<em>Answer:</em>
<em>1. One of the students </em><em><u>is</u></em><em>(was/is) talking.</em>
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<em>2. My friend and his father </em><em><u>have</u></em><em> (are/is) a meeting that is tomorrow.</em>
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<em>3. The novelist and poet </em><em><u>were</u></em><em> (was/were) dead.</em>
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<em>4. Ravi as well as his brother </em><em><u>plays</u></em><em> (play/plays) cricket.</em>
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<em>5. Nobody </em><em><u>knows</u></em><em> what happened to her. (know/knows)</em>
<em>❀Hope this helped you!❀</em>
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