To give you an example of "has been ---ing": "Leo has been learning Japanese for the past 10 years" "Leo has been meeting famous people all his life" This implies he was doing it in the past, and it continues now (we get this idea without adding anything more to the sentences). In your example, "has been ---ing" doesn't work because the activity was in the past and is finished. One clue is from the word "historical" (relates to the past; living people might be important but are not usually historical until they have died!) Another clue is "during his life", which fits with "has met". This is a bit complicated because the next part of the sentence says "and he looks forward to meeting many more" which tells us that the activity will continue. However, this idea is ONLY introduced with this second part of the sentence. From a grammar perspective, the first half of the sentence describes a finished activity. You could also imagine this as two separate sentences: "Leo has met many important historical figures during his life. He looks forward to meeting many more."

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. Examples: 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. Examples: 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.

There is no requirement that a person be alive to correctly use the present perfect tense. Example: (Eulogy at a funeral): My father has always been a source of inspiration in my life. Since my father's inspiration is still relevant in my life, I can use the present perfect.

Leo is still alive. These actions (meetings) started in the past, and as he is still alive there could be more, in the present and in the future. For this use case, English has the present perfect tense - here, "has met". The next best choice would be A - which is entirely a possibility here, although B would normally be preferred. See https://learnenglish.britishcouncil.org/english-grammar-reference/present-perfect and https://www.perfect-english-grammar.com/present-perfect-or-past-simple.html For choice C, this tense is called the present perfect continuous. This has the slightly different sense whatever started in the past is still continuing in the present - and is going on today, right now. We don't normally choose a continuous tense unless something really is continuing, and we want to emphasise that (or, informally, for fun, in slang). So here the normal choice would be "B". https://learnenglish.britishcouncil.org/intermediate-grammar/present-perfect-simple-and-continuous

during his life means his life from the past until now, so B is correct. and you don't know in the future, he will have any important historical or not. what if he dies tomorrow??