问题：
[多选题]A good conclusion usually consists of_________.
Aa brief summary of main points
Ba short conclusion if necessary
Cshowing gratitude to the audience for their presence
Dleading up to a question and answer session
[多选题]A good conclusion usually consists of_________.
Aa brief summary of main points
Ba short conclusion if necessary
Cshowing gratitude to the audience for their presence
Dleading up to a question and answer session
