Which question can be answered by an experiment? A)
Do sugar substitutes cause cancer?
B)
Did an ice age kill off the mastodons?
C)
What caused the extinction of the dinosaurs?
D)
Are all people susceptible to the Hunta virus?

Options A and D

Explanation:

because options B and C are part of history, you can learn about them on the internet plus there is no way we can experiment with those options. Options A and D may be right because of course, we can experiment if sugar substitutes cause cancer, and if all the people are susceptible to the Hunta virus.

  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-