The entire thing was about race. Only African people were targeted.
this website should help
https://en.wikipedia.org/wiki/Parliament_of_the_Cape_of_Good_Hope
It's not A, as they simply aren't forced to.
It's not C, as Africa is not 'just' a colony; infact, empires and therefore colonies are no longer allowed among the UN.
D is incredibly stupid.
So, B.