<<我的一篇舊文>>
當附屬名詞子句的主詞緊接在主要子句的「及物動詞」之後時，如果這個主詞容易被誤認為是之前的及物動詞的直接受詞，這時不要省略that。
Example:
When a researcher discovers a new strain of the flu could threaten a large segment of the population, the ethics panel determines whether the public should be notified immediately.
這句在讀的時候，因為”... discovers ...” 是及物動詞，於是很自然的會把緊接在後面的名詞當成是這個動詞的受詞: “....discovers a new strain of the flu...”--- "....一個研究員發現了新品種的病毒..."，但是當繼續讀到"could”時才會發現不對勁(接下來的內容也不需要拆解了，因為文法上不正確)，然後(對英語人士來說)才會知道之前的名詞應該是"could threaten”的主詞，也就是( a new strain of the flu could threaten a large segment of the population)這整個名詞子句才是”... discovers ...”的受詞，然後意思上是"一個研究員發現了一件事”，什麼事呢？"一種新品種病毒可能會威脅到......”。這兩者的差別在於，一個是在講這研究員是發現這個新品種病毒的人，一個則是講這研究員發現此種病毒可能有很大的殺傷力，但是這新品種病毒是誰發現的就沒有清楚交代同時也不是重點。所以這時候讓意思清楚的改進方法就是不要省略that:
When a researcher discovers that a new strain of the flu could threaten a large segment of the population, the ethics panel determines whether the public should be notified immediately.
以下則是另外幾個例子。不應該省略的that特別標出來放在方括弧裡。
Mr. Green noticed [that] the kids he continued to bring to practice with him improved greatly.
But on board his flight to Los Angeles, he found [that] the promised seat-back TVs were missing, and the bottled water ran out halfway there.
當這種緊接在及物動詞後面的名詞子句有兩個或是三個以上時，要注意平行架構的使用。
以下的例子都是用同一句，然後比較有無that的差別。
主要子句(基本句型): I realized (‘this’) and (‘that’)
第一個附屬名詞子句(相當於 ‘this’): (I was going to be late for the meeting )
第二個附屬名詞子句(相當於 ‘that’): ( there was nothing I could do )
Faulty: I realized I was going to be late for the meeting and that there was nothing I could do.
(這句只有後頭的名詞子句有that)
Correct: I realized that I was going to be late for the meeting and that there was nothing I could do.
(兩者都有that)
Correct: I realized that I was going to be late for the meeting and there was nothing I could do.
這例子的話，因為前半部的名詞子句前頭有that，所以後頭的that可以省略掉。一個很簡單的理由(也是很普遍的用法)就是and後頭的子句沿用了前頭的that。
(Note)這篇的英文部份以及主要觀念/架構出自:
"The Writer's Digest: GRAMMAR DESK REFERENCE", Gary Lutz & Diane Stevenson.
Publisher: Writers Digest Books; Desk edition (June 15, 2005)
ISBN: 1582973350
中文部份除了翻譯之外，一些進一步的解說主要是用我自己的話寫出。中英文有矛盾的地方以英文原書內容為主。
