Need with this question .

which option accurately describes an unbalanced force?
1.three rows of cement blocks from a foundation for a house, and the house rests on its foundation.
2.the force of a house pressing down on its foundation of cement blocks is 3,000 n
3.each cement block supports a 2-n force, but when the foundation is built in a staggered pattern it can support 2,000 n
4.a 2-n force presses down on the cement block at the same time as a 1.5-n force presses up on the cement block

One way in which the useful metal copper is produced is by dissolving the mineral azurite, which contains copper(ii) carbonate, in concentrated sulfuric acid. the sulfuric acid reacts with the copper(ii) carbonate to produce a blue solution of copper(ii) sulfate. scrap iron is then added to this solution, and pure copper metal precipitates out because of the following chemical reaction: (s) (aq) (s) (aq) suppose an industrial quality-control chemist analyzes a sample from a copper processing plant in the following way. he adds powdered iron to a copper(ii) sulfate sample from the plant until no more copper will precipitate. he then washes, dries, and weighs the precipitate, and finds that it has a mass of .