Everyone dreams about 20 percent of their sleeping time. 23 people who say they never dream show about 20 percent of REM sleep. 24 these “non-dreamers” do their sleeping in a laboratory 25 researchers can wake them up and ask them whether they were having dreams the moment before, it 26 that they dream as much as others.
答案：(B) where
where 引導地方關係子句，修飾先行詞 a laboratory（在……的實驗室裡）；that／which 通常不這樣引導子句來表達「在……裡」的地點語意，who 指人，不合先行詞 laboratory，只有關係副詞 where 正確。
本題大考中心未公布逐題答對率，以下不談數據，只談觀念。
that 與 which 是你最熟的兩個關係代名詞，看到空格前面有個名詞、後面接一串話，很容易就在這兩個之間挑。但這一格填哪一個，不是看你熟不熟，是看後面那個子句還缺不缺東西。
四個選項都是能帶出子句的字，先用分流判準看空格前面接的是名詞還是動詞：前面是 a laboratory（名詞），所以這是回頭補充說明那個名詞的關係子句，不是間接問句。接著數子句成分：researchers can wake them up and ask them whether they were having dreams ——主詞是 researchers，動詞是 can wake 與 ask，受詞是 them，成分一個都不缺。既然不缺，that、which 這種一定要在子句裡占一個位置的字就都進不來。剩下的 where 是關係副詞，本身不占句子成分，只代替一個表地方的介系詞片語。還原一次就清楚了：in a laboratory, and in the laboratory researchers can wake them up（在一間實驗室裡，而在那間實驗室裡研究人員可以叫醒他們），把 in the laboratory 換成 where。同判準的題目題庫裡有好幾題：92 年第 25 題、98 年第 23 題，都是先行詞是地方、子句成分已滿，答案就是 where。
that、which：關係代名詞，進到子句裡一定要當主詞或受詞，本句這些位置都滿了，塞不進去。who：只用來指人，而先行詞 a laboratory 是地方，一眼就能刷掉。
a laboratory where …（一間……的實驗室）、the place where …（……的地方）、the reason why …（……的原因）、the time when …（……的時候）、have a dream（做夢）、the moment before（前一刻）。
Basically, there are two kinds of sleep. One is Rapid Eye Movement (REM) sleep. In 21 , the brain waves of a sleeping person are similar to those of a waking person, and the eyes move about rapidly under the closed lids. 22 kind of sleep is Non-Rapid Eye Movement sleep.
Scientists have discovered that dreams happen mainly in REM sleep. Everyone dreams about 20 percent of their sleeping time. 23 people who say they never dream show about 20 percent of REM sleep. 24 these "non-dreamers" do their sleeping in a laboratory 25 researchers can wake them up and ask them whether they were having dreams the moment before, it 26 that they dream as much as others.
Events in daily life sometimes occur symbolically in dreams. 27 , a boy is having difficulties on the school playground because a bigger boy keeps bullying him. He may dream at night of being alone in the playground, 28 a lion. At other times the dreaded event from daily life simply occurs in a dream in its real-life form; 29 , the boy dreams of being bullied by the bigger boy.
30 scientific research, we have known more about the relationship between sleep and dreams. However, why a dream will take a certain symbolic form is still a mystery.