Why do warehouse workers move heavy boxes around on carts with wheels?  

We know that sliding require more force that rolling

because in rolling friction is very less

as small portion of surface are in contact so the experience less friction than sliding

so it is easy to roll an object than sliding the same mass

that is why we use round shape wheel

which is easy to move

and because of that we use cart with wheel to move heavy loads

we can carry heavy loads easily in carts

if we try to lift it or slide, it needs more work to be done

but in cart we can carry heavy loads easily

multiple

real, smaller and upside-down.   so the answer should be b.