一、主语+谓语（S+V）

这类句子有一个共同特点，即句子的谓语都能表达完整的意思。

谓语动词是不及物动词，后面可以跟副词、介词短语、状语从句等。

例如：

An accident that occurred in the skies over the Grand Canyon in 1956 resulted in the establishment of the Federal Aviation Administration （FAA） to regulate and oversee the operation of aircraft in the skies over the United States, which were becoming quite congested. （剑8 Test 1Passage 2 ）

句子结构分析：

这句话的主干是An accident resulted in the establishment of the Federal Aviation Administration （FAA）。

主谓结构式An accident resulted，后面跟得是介词短语。

That引导定语从句修饰An accident，to regulate and oversee…表示目的，which引导非限制性定语从句修饰the operation of aircraft。

二、主语+谓语+宾语（S+V+DO）

这类句子的谓语都是实意动词，也都是及物动词，表示主语发生的动作，但是，后面必须跟一个宾语，也就是动作的承受者，才能表达完整的意思。

例如：

They based their calendars on three natural cycles: the solar day, marked by the successive periods of light and darkness as the earth rotates on its axis; the lunar month, following the phases of the moon as it orbits the earth; and the solar year, defined by the changing seasons that accompany our planet's revolution around the sun.

（剑8 Test 1Passage 1 ）

句子结构分析：

这句话的主语是They，谓语是based，宾语是their calendars，后面是on引导的介词短语。

冒号后面的三个并列结构：the solar day, the lunar month and the solar year，是对three natural cycles的解释说明。

that引导定语从句修饰changing seasons changing seasons。