题目内容：

Simple things that are super complex

● Defining (定义) the word “the” is really difficult.

The word “the” is one of the most common words in the English language and most of us have probably never stopped to think about how strange of a word it actually is. A dictionary lists more than twenty different ways the word can be used in a sentence correctly, which makes an exact definition of the word much more difficult to explain.

● There’s no theory (理论) accepted by everyone on how bikes work.

Bicycles have existed (存在) for over 100 years, and scientists have been discussing about how exactly they work, or more specifically, how they stay upright, almost since they were first invented. But there’s no exact answer to it. And because bicycle dynamics (动态) isn’t exactly an area of science into which researchers like to spend time, it’s highly impossible that we’ll know for sure anytime soon.

● Yawning (打哈欠)

Yawning is a puzzling phenomenon (现象). Even that act of talking about it is simple enough to make some people do it. There is really no other bodily function quite like it. In fact, there is no theory for we yawn, which is agreed upon by everyone. As for why yawning is contagious (传染), no one knows that either.

阅读以上信息，用恰当的词完成下面的表格，每空一词。

The word “the”	● It is one of the most words in English language, most of us 1. on thinking about the word. ● There are 2. twenty different ways of its usage in the dictionary, it is still difficult to make an exact definition of this word.
Bicycle	● Bicycle have existed for over 100 years and have been 3. how exactly they work. ● Researchers don’t like to spend time on how bicycles and 4. react to each other.
Yawning	● It’s a puzzling phenomenon which is simple enough to make some people do while talking about it. ● No other bodily function is like yawning. ● No one knows the 5. — why yawning is contagious.