1. PART A: Which of the following best describes the author's main claim in the text
O A Water scarcity is not something that humans have
any control over, as it is caused by natural events,
B Humans can reverse the damage they have inflicted
on the Earth's water supplies if they reduce their
pollution output
C Widespread water scarcity threatens the right that
all humans should have to access dean drinking
water, as it is essential to live,
D Water scarcity is an issue primarily caused by
humans that needs to be addressed by humans.

explanation: no but i do not usually comment

  the   balanced   equation   for   reaction of   ca metal   with   o2 to   produce   cao   is as below

2 ca+ o2→ 2 cao2

  explanation

the reaction is   balanced     since the   number of atoms   in reactant side is   equal to   number of atoms   in   product side.   for   example   they   are 2   atom of   ca in   reactant   side   and   2   atoms of ca   in   the product side.

  the   process   is a   meet the   requirement   of   redox   reaction because :     calcium   is   oxidized   from   oxidation state 0   to 2+   while   oxygen   is reduced from   oxidation   state   0   to 2-

i have no clue hope you find the answer