Which statement about atoms is correct A atoms contain protons and electrons in the nucleus
B Neutrons are negatively charged
c protons are positively charged
D the nucleon number is the number of neutrons

Protons are positively charged is the correct statement about an atom

I've also corrected the other statements

Atoms contain protons and neutrons in their nucleus

Neutrons posses no charge and are neutral

The nucleon number is the total number of protons and neutrons in a nucleus

a  solution  is always transparent, light passes through with no scattering from solute particles which are molecule in size. the  solution  is homogeneous and does not settle out. a colloid is intermediate between asolution  and a  suspension. while asuspension  will separate out a colloid will not.

  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-