I. 联合复句 Compound Complex Sentences
Complex sentences consist of two or more simple sentences called clauses. Complex sentences are used to express a complete thought and are spoken with a certain intonation. For example:
小王刚走，老张就来了。风停了，雨也不下了。
如果中文太难，我就不学了。
她的衣服很漂亮，我的不好看。
Two or more clauses in a complex sentence are separated by a pause when spoken, and indicated by a comma or a semicolon in writing. The sentence is spoken as one entity. If the clauses share a common subject, then the subject does not have to be repeated. For example:
马克会英文，马克会西班牙文，马克不会法文。
我想省钱，我不想买太贵的电脑。
Here are the correct sentences:
马克会英文、西班牙文，不会法文。
我想省钱，不想买太贵的电脑。
In a complex sentence, clauses have various relationships that are often denoted by conjunctions. For instance:
因为没有买到火车票，所以他们得在旅馆住一天。
不但我们喜欢那个歌星，而且我妈妈也很喜欢他。
既然你觉得物理太难了，你今年就别选这门课了。