複數與介係詞：每篇作文都會重複出現的錯誤

In Mandarin, 三本书 uses the same noun 书 as 一本书 — quantity is carried entirely by the number and measure word, and the noun itself never changes. English instead requires the noun to change ("three books") independent of whether a number is even present: "many students", "few resources", "most countries" all need the plural noun even though no digit appears. Under time pressure, Chinese speakers reliably drop the -s specifically in two places: after quantity words other than a literal number (many, several, various, a range of), and on nouns separated from their quantity word by other words ("the three most important factor" — the adjective "important" sits between "three" and the noun, making it easy to forget the noun needs marking too). The fix during proofreading is mechanical: find every plural quantity word and trace forward to its noun, no matter how many words sit between them.

在中文裡，「三本書」和「一本書」用的是同一個名詞「書」——數量完全由數詞和量詞承擔，名詞本身從不改變。英語則要求名詞本身變化（"three books"），而且這種變化與句子裡是否出現具體數字無關："many students"、"few resources"、"most countries" 這些說法即使沒有出現具體數字，名詞也必須用複數。在時間壓力下，中文母語者最常在兩個地方漏掉 -s：一是跟在「many、several、various、a range of」這類非具體數字的數量詞後面；二是名詞與數量詞之間被其他詞隔開的時候（比如 "the three most important factor"——形容詞 "important" 插在 "three" 和名詞之間，很容易讓人忘記名詞也需要加複數標記）。校對時的解決方法很機械：找出每一個表示複數概念的數量詞，一路向後追蹤到它所修飾的名詞，無論中間隔了多少個詞。

Prepositions cause more errors than almost any other word class because Mandarin coverbs (在, 于, 关于, 依赖) do not map one-to-one onto English prepositions — the mapping has to be memorized case by case, not translated. Four patterns cover a large share of exam errors. Time: use "in" for months/years/decades ("in July", "in 2020"), "on" for days and dates ("on Monday", "on July 3rd"), "at" for clock times and a few fixed points ("at 9 a.m.", "at night"). Place follows the same logic: "in" for enclosed areas or large regions ("in Taipei", "in the room"), "on" for surfaces ("on the table", "on page 12"), "at" for specific points ("at the entrance", "at the corner"). Two verbs are worth memorizing as exceptions because they take no preposition at all where a direct Mandarin translation would suggest one: "discuss" (not "discuss about") and "attend" (not "attend to" when it means "go to" an event). And "depend on" is the fixed pairing — never "depend to" or "depend for".

介係詞是造成錯誤最多的詞類之一，因為中文的介係詞/動詞（在、於、關於、依賴）與英語介係詞並非一一對應——這個對應關係必須逐個記憶，而不能靠直譯。有四類模式涵蓋了考試中相當大一部分介係詞錯誤。時間：月份、年份、年代用 "in"（"in July"、"in 2020"）；具體的日子和日期用 "on"（"on Monday"、"on July 3rd"）；鐘點時刻和少數固定說法用 "at"（"at 9 a.m."、"at night"）。地點遵循同樣的邏輯：封閉區域或較大範圍用 "in"（"in Taipei"、"in the room"）；平面表面用 "on"（"on the table"、"on page 12"）；具體的點用 "at"（"at the entrance"、"at the corner"）。有兩個動詞值得當作例外單獨記住，因為直譯成中文會讓人以為需要介係詞，但英語裡它們後面完全不加介係詞："discuss"（不是 "discuss about"）和表示「去參加」某活動時的 "attend"（不是 "attend to"）。而 "depend on" 是固定搭配——絕不能說成 "depend to" 或 "depend for"。