The integration of Major League baseball was
viewed to be a potential threat to revenue because Major League clubs rented their ballparks when they traveled to Negro League teams.
A)
viewed to be a potential threat to revenue because Major League clubs rented their ballparks when
they traveled to Negro League teams.
"Viewed as" is the correct idiom. So are the Major League clubs travelling to Negro League teams? No, they're renting the ballparks! Definitely a change in meaning.
B)
viewed to be potentially threatening since Major League clubs rented their ballparks when they traveled
to Negro League teams.Same as A. Also worse because we lost the crux of the sentence about revenue....
C)
viewed as potentially threatening to revenue since Major League clubs rented their ballparks when
they traveled to Negro League teams.D) viewed as a potentially threatening
situation to revenue, for many Major League clubs rented their ballparks to Negro League teams when they traveled.
So many issues here. "Potentially threatening situation to revenue" is extremely unnecessary (E says it better). "They" refers to Negro League teams.
E)
viewed as a
potential threat to revenue because many Major League clubs rented their ballparks to Negro League teams when they traveled.
Best of the rest.