How did destroying the city of thebes prove alexander to be more than a mere boy?

The correct answer to this open question is the following.

When Alexander destroyed the city of Thebes, he proved to be more than "a mere boy," as the Greeks considered him. But when he led the troops to victory, he showed he had the skills, abilities, and leadership of a true warrior and strategist. This made people really respect and trust him, and word of mouth spread over other regions. He burned all the houses in Thebes and sent a clear message to his enemies.

(e) a major consequence of the election was that several southern states

abraham lincoln  (february 12, 1809  – april 15, 1865) was an american statesman, politician, and lawyer who served as the 16th  president of the united states  from 1861 until  his assassination  in april 1865. lincoln led the nation through the  american civil war, its bloodiest war and its greatest moral, constitutional, and political crisis.[2][3]  he preserved the  union,  abolished slavery, strengthened the  federal government, and modernized  the u.s. economy.