It is nitrogen dioxide.
And the o should be capitalized
Answer: 10
Because I counted back 10 times on the middle of the number line marks and when I got to 1950 I noticed I counted back 10 times each Line
Here are some contrubition they did to the world
Olympic games
Democracy
Hippocratic Oath
Philosophy (Aristotle, Socrates, Plato...)
Ionian, Doric and Corinthian architectural styles
Theatre styles (drama, comedy, tragedy, tragicomedy).
Literary classics (Iliad & Odyssey, myths, fables, poetry and mythology)
Roger Bannister is the answer
Without Washington's help there would be no United states for other presidents to overlook