Aball is thrown in the air. the ball goes up, then changes direction and falls down. why does the ball fall down? gravity pushes the earth up. gravity makes the ball lighter. gravity stops working. gravity pulls it down.

Read the given expression. x = number of protons − number of core electrons which of the following explains the identity of x and its trends across a period? x is the effective nuclear charge, and it remains constant across a period. x is the screening constant, and it remains constant across a period. x is the effective nuclear charge, and it increases across a period. x is the screening constant, and it increases across a period.

Astudent conducts an experiment to determine how the amount of water given to a plant affects its growth. what is the independent variable for this experiment?

At element makes up all organic compounds?