The correct answer will be C. Carbon and Oxygen because these both are non metals and non metals react colvalently (i.e share electrons) while when metals react with a non metals they react ionically (i.e lose and gain electrons)
3. Atoms change into other atoms in chemical reactions.
The idea that you can transform one element into another was called alchemy, and was proven untrue a long time ago.
B) some planets revolve backwards
Maybe number 2. 20 hope that helps