What two hydrogen atoms bond with one oxygen atom to form water what happens to the electron

Iknow the answer is a but i don't know why

How have the greenhouse gasses increased from the year 2000 to 2018

What effect would average population growth have on land usage? a. urban use of land would rise to more than 30 percent of available land. b. industrial use of land would rise to more than 30 percent of available land. c. the percentage of available land used as cropland would stay the same. d. cropland would fall to about 10 percent of available land.