Hundreds of years ago, it was believed by many that our solar system was Geocentric. This means that Earth is at the center of the solar system, with the Sun and other planets orbit around it. Today, the solar system is now thought to be Heliocentric.

What does this mean?
A) The Sun and other planets orbit Earth.
B) Earth and all the other planets orbit the Sun.
C) The other planets orbit Earth, and Earth orbits the Sun.
D) The Sun orbits Earth and the other planets orbit the Sun.
Eliminate

B) Earth and all the other planets orbit the Sun.

Explanation:

A) This one is basically what people used to think, that the sun and other planets orbited around Earth. We know now that this is not true.

C) We know that no planets orbit around Earth.

D) The Sun does not orbit around Earth, the Earth orbits around the Sun.

2h2o2--> 2h2o + o2

this reaction is of the spontaneous decomposition of hydrogen peroxide down into water and oxygen.

add 2 molecules of hydrogen peroxide and 2 molecules of water. since oxygen is naturally diatomic, the total number of atoms of each element is now the same on both sides of the equation so it is balanced.

this may not be entirely correct but let me know.

a corroding iron, if that's one of your choices