16. It is believed ________ causes sleep problem. So it’s better not to drink coffee before going to bed.
(A) too much caffeine which
(B) that too much caffeine
(C) it is too much caffeine
(D) too much caffeine

這題考的是 名詞子句的引導詞結構：

題目句子：

It is believed ________ causes sleep problem. So it’s better not to drink coffee before going to bed.

✅ 分析關鍵語法：

• 「It is believed ___ causes sleep problem」

• 這是典型的 It is believed + [名詞子句] 結構

• 名詞子句作為 believed 的真正受詞，所以需要用 that 子句 來引導這個完整的句子：「太多咖啡因會導致睡眠問題」

? 選項解析：

(A) too much caffeine which ❌

→ "which" 是關係代名詞，但這裡不是形容名詞，而是要引導一個 完整的主詞從句，語法錯誤。

(B) that too much caffeine ✅

→ 正確！完整句為："It is believed that too much caffeine causes sleep problem."
→ 這是標準的 名詞子句語序。

(C) it is too much caffeine ❌

→ 重複主詞 "it is..."，句子會變成語意混亂、結構不完整。

(D) too much caffeine ❌

→ 少了連接詞 "that"，讓整句變成斷句：It is believed too much caffeine causes... → 雖然口語中偶爾會出現，但在正式語法中不夠完整、不正確。

✅ 正確答案是：

(B) that too much caffeine