I think the second option is the best (by making the ramps height and length equal) because the first option will require more pushing, the third option will only make the ramp lighter which could cause it to not stay in place, the last option would make it harder to push the boxes up because the rubber will make it harder to slide the boxes up. I hope this helps:)
An absorptive heterotroph is an organism which secretes enzymes externally into its environment to digest organic materials which are then absorbed.
First one, disease causing microorganisms
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