A、She failed to arrive at the airport on time. B、David promised to go on the trip in her place. C、Something unexpected happened

W: What is it, Bob? You sounded pretty serious on the phone. Have we still got a budget problem?
M: I don’ know. I hope not. The meeting’s on Friday. But that’s not what I want to talk to you about. Er, close the door, will you? It’s Marsha.
W: Marsha? What about her?
M: I’m worried. I don’t know what to do. She’s just not performing. We may have to let her go.
W: Fire her? She’s been with us a long time, Bob. If she leaves, it’ll be a big loss to us. She’s done really excellent work.
M: Yes. But lately, the last month or so, in fact, there have been a lot of problems. She’s changed. Not only does she have a tendency to be moody all the time, but she misses appointments, doesn’t follow through on projects, and doesn’t seem to plan anything till the last minute.
W: Em, did she ever explain why she didn’t show up for the Denver trip?
M: No. She said she was sorry and that it wouldn’t happen again. Something about a mix-up on arrangements to get to the airport. Now, whenever anybody mentions the subject to her, she just goes silent. I don’t know. Thank goodness. David pulled us out of the hole on that one.
W: Yes, he did a really fine job, filling in for Marsha like that at the last minute.
M: I don’t think it was the first time he’s had to do that. If we knew all the facts, I think we’d find that he’s been covering for Marsha on quite a few projects.
9. What did the man do before he came to see the woman?
10. What does the man say about Marsha?
11. How did Marsha explain why she didn’t show up for the Denver trip?
12. What does the man say about David?