During such breaks, the mind turns inward, 19 it can subconsciously puzzle over subtle meanings and connections.
答案：(C) where
where 引導關係副詞子句，先行詞是前面的 the mind turns inward 所形成的「內在境地」；which 之後的子句已完整、無空缺，if 與 but 也無法與逗號前的敘述構成合理邏輯。
答對率 28%。
where 在你腦中大概只能指「地方」——公園、學校、城市；一看到前面沒有具體地點，就把 where 排除掉。事實上 where 引導的關係副詞子句，先行詞不必是實體場所，也可以是抽象的「情境、境地、狀態」。
the mind turns inward（心思轉向內在）這句話造出的正是一個抽象的「內在空間」，後面的 it can subconsciously puzzle over subtle meanings and connections（在其中，心思能潛意識地琢磨細微的意義與連結）就發生在這個空間裡，用 where 承接最自然。
關係代名詞 which 在子句裡必須擔任主詞或受詞，也就是子句會「缺一角」；本句 it can subconsciously puzzle over… 主詞 it、動詞 puzzle over、受詞 subtle meanings 樣樣不缺，沒有位置留給 which。這是判斷 where／when 與 which／that 最可靠的方法：子句完整就用關係副詞，子句缺主詞或受詞才用關係代名詞。
if 引導條件，但前後不是條件關係；but 表轉折，然而「心思轉向內在」與「琢磨細微意義」是順承而非對比。
國中學過 This is the house where I was born.，本題只是把具體的 house 換成抽象的心理境地。同類的還有 a situation where…（在…的情況下）、cases where…（在…的案例中）。
a situation／case where…（在…的情況／案例中）、the reason why…（…的原因）、the time when…（…的時候）、puzzle over（苦思）、turn inward（轉向內在）。
It has long been assumed that creativity is some unusual trait enjoyed by the few. However, according to a wide array of scientific and sociological research, creativity is 16 a sign of rare genius than a natural human potential. Thus, it can be nurtured and encouraged.
It is believed that taking breaks from a problem can help 17 a moment of insight or stimulate new ideas. Unconventional solutions can also be explored. That is why some of the most successful companies in the world, such as 3M and Google, encourage their employees to 18 all sorts of relaxing activities, such as playing pinball and wandering about the campus. During such breaks, the mind turns inward, 19 it can subconsciously puzzle over subtle meanings and connections.
Another way to increase creativity is to take risks. This is because many breakthroughs come up when people venture 20 their usual routines or areas of expertise. This can be done by, for example, learning new skills or traveling to new countries.