How do i know which one to use, a comma , semicolon or neither

assuming the underlined sentence is:

"approximately 250 big name scientists will be winging their way to washington, d.c. "

the correct answer would be:

d) approximately 250 well-known scientists will be arriving in washington, d.c.

the word "big-named" is making reference to a well known, successful important or famous person, product or company, in this case, given is an international research institute convention these ones are scientists.

the answer's:

(a) its negative connotation indicates that enslaved people had to work like robots instead of human beings.

external conflict because internal conflict is having a conflict within yourself. hope this ! : )