汽油机的一个工作循环分为四个冲程，每个冲程都伴随着能量的转移或转化，其中主要将机械能转化为内能的冲程是（  ）

阅读下面这首古诗，回答下面两题。
                                                                                                                                            闽中秋思
                                                                                                                                      （唐）杜荀鹤
                                                                                                                      雨匀紫菊丛丛色，风弄红蕉叶叶声。
                                                                                                                      北畔是山南畔海，只堪图画不堪行。