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

the word that best describes martin luther king jr.'s tone in the video is dignified

martin luther king, jr. was a social activist and baptist minister who played a key role in the american civil rights movement from the mid-1950s until his assassination in 1968. the video shows his manner and attitude having or showing a composed or serious manner that is worthy of respect so dignified is the correct answer

option number c is the right answer.