I need help please which option is it ?

D.

Explanation:

The first two blocks are sinking below water while the third is rising. This means the first two are denser than water and  the last is not as dense as water.

I would say object 3 is less dense than objects 1 and 2.

Explanation:

I would say object 3 is less dense than objects 1 and 2 because it is floating higher than the other in the water, and a object that is more dense will sink more and a object that is less dense with float more.

Hope this helps.

answer:

the reaction is type of combination reaction.

explanation:

on the product side, there are 2 molecules of bonded to fe   which means one atom of fe are combined two molecules of . so, balanced chemical equation becomes :

this reaction follows the reaction type of combination reaction. a combination reaction is defined as chemical reaction in which reactants combines together to form a single product.