This specific genocide (there were also other kinds of genocide in the history, such as the Armenian Genocide) is known as the Holocaust (Holocaust refers mostly to the Jewish population). Around 6 million people died in this genocide, and in this number half are Polish Jews.
<h2>B: the amount of moisture in the Earth’s atmosphere. </h2>
As by definition humidity is the concentration of water vapours in the air. So the best answer is B.
