How do the nuclei of different isotopes of an element vary?

Because isotopes of an element have a different number of neutrons, they also have different mass numbers.

your answer would be fusion

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