Answer:
Iron is the densest out of the given options.
Explanation:
Oxygen
1.429 g/L
Water
1000 g/L
Hydrogen Peroxide
1450 g/L
Iron
7874 g/L
Iron Oxide
5240 g/L
Answer:B) a reactant that undergoes reduction
Explanation:
Oxidation reaction is defined as the reaction in which a substance looses electrons. The oxidation state of the substance increases during oxidation.
Reduction reaction is defined as the reaction in which a substance gains electrons. The oxidation state of the substance gets reduced during reduction.

Overall reaction: 
The substance M which itself gets oxidized, reduces other and is called as reducing agent. The substance N which itself gets reduced, oxidizes other and is called as oxidizing agent.
gold is usually found in pure form because it is not reacting with other chemicals naturally.
Ultraviolet as ultraviolet light waves are around 420 nm like stated in the photo
Answer:
water was added to powdered rock
Explanation: