"since we knew" vs "since have known"

[Sitifan]

1. We have been sad since we ____ the news.
(A) have known (B) knew
2. He has been a boss since we ____ him.
(A) have known (B) knew
The answer to #1 is B; but the answer to #2 is A.
Why? What's the difference between them?
_________________
Thank you very much for your reply.

[Yankee]

Hi Sitifan

The verb 'know' seems a little odd as a choice of words for sentence 1. I'd prefer this:
1. We have been sad since we heard the news.
- Use the simple past because "heard" refers to a specific and finished point in time.

For sentence 2, option (A) is best:
2. He has been a boss since we have known him.
- Use the present perfect because, although "knowing him" began in the past, "knowing him" also continues up until now.
.