Answer:
C. It is Britain’s duty to spread European ways and customs around the world.
Step-by-step explanation:
The part where it mentions "If there be a God, I think that what he would like me to do is to paint as much of the map of Africa British red as possible." implies that Rhodes wants to spread European customs to other places. I don't think it's A because I don't really see where the passage mentions anything about manufactured goods. It's definitely not B or D because I think those just don't really make any sense.
I hope this helps! o(〃^▽^〃)o