如图所示，竖直平面内固定着一个滑槽轨道，其左半部分是倾角为θ=37°，长为l=1m的斜槽PQ，右部是光滑半圆槽QSR，RQ是其竖直直径，两部分滑槽在Q处平滑连接，R、P两点等高，质量为m=0.2kg的小滑块（可看作质点）与斜槽间的动摩擦因数为μ=0.375，将小滑块从斜槽轨道的最高点P释放，使其开始沿斜槽下滑，滑块通过Q点时没有机械能损失，求：

补全对话, 其中有两个多余选项。

(D=Darren, C=Carol)

D: Hi. Carol! ____

C: Oh, hi, Darren. I’m just getting ready for the Red Nose Day concert tomorrow.

D: Oh, really? Well, I’m free this afternoon. ____

C: Actually, I’ve nearly finished. Jim and I are going to put up some ads later, though. Could you please help us with that?

D: ____

C: That’s wonderful! Oh, there’s one more thing. Would you mind coming early tomorrow to help sell tickets at the door?

D: Not at all. ____

C: Around six would be great.

D: OK. ____

C: Great.

什么叫合纵连横？