Question

ゲスト

黄色の下線部で引いた文についてなのですが、in whichの、in の意味がわかりません。なぜここにinがあるのでしょうか？

o bored, sleepy, or because our bodies are tired、

 

[6| Still another theory is that yawning started with our ancestors. When you yawn,
you also show your teeth。 Some scientists believe that this was a way in which ancestors

frightened others,  such as when a ion roarsY Onetheory states that Lyaming may have

前置詞と関係代名詞