A: So listeners can stay awake and alert.
<span>1. Mary Todd Lincoln's life was marked by three traumatic episodes: the deaths of sons Willie and Tad and the assassination of her husband, the president.
</span><span>2. Most wildflowers are transient they wilt soon after they are picked.
</span>
3. Years of drought in north central Africa have created a (n) aberration of refugees numbering in the thousands.
4. A transitive verb carries action from the doer to the receiver, as in "The batter smacked the ball."
5. Newspapers published a (n) obituary of Emperor Hirohito of Japan the day after his death in 1989.
<span>6. In spite of its name, the French Quarter of New Orleans retains a Spanish colonial ambience for the years it belonged to Spain.</span>
Answer:
No one really knows
Explanation:
Scientists have been reaserching this for many years, but still, no one has found the answer.
Can u make the question clear?