Think of it this way, the present perfect is used similarly to the simple past except that the present perfect
is used when the event is still relevant in the present moment.
I lived in France four years. (I don't live in France anymore.)
I have lived in France four years. (I still live in France.)
Use the present perfect continuous for continuous actions.
Leo has been meeting many important historical figures SINCE arriving in Berlin.
Leo has been meeting many important historical figures ALL MORNING.
In my opinion, answer C is possible because the word DURING implies a continuous action. However, it's not likely. It's more common to use the present perfect in this situation because, presumably, Leo has had times during his life when he wasn't meeting important historical figures, so the act of meeting them isn't really a continuous action throughout his lifetime.