Who determined that the moon was not a source of light but reflected light? a. Bacon
C. Galileo
b. Kepler
d. More

the answer is Galileo buttt a scientist much earlier then Galileo named Anaxagoras determined it fist but the credit was given to Galileo.

john maynard keynes developed new economic theories in response to the stock market crash of 1929. great depression of the 1930s. first and second world wars. economic boom of the 1950s.

2018 means 2018 ce or common era

there have been other eras too including bce, which included way more years.