假設語氣
Subjunctive Mood
假設語氣用來表達與事實相反的假設、願望或虛擬情況。根據假設的時間不同（現在或過去），使用不同的動詞形式。這是學測高頻考點，務必掌握各種假設語氣的句型。
文法規則說明
【Contrary to Present Fact】與現在事實相反的假設：If 子句用過去式（be 動詞一律用 were），主要子句用 would/could/might + 原形動詞。表達的是「如果現在...（但實際上不是）」的意思。 公式：If + S + V-ed/were, S + would/could/might + V
【Contrary to Past Fact】與過去事實相反的假設：If 子句用過去完成式（had + V-pp），主要子句用 would/could/might + have + V-pp。表達的是「如果當時...（但實際上沒有）」的意思。 公式：If + S + had + V-pp, S + would/could/might + have + V-pp
【Wish / As if / As though】wish 後面的子句用假設語氣：與現在相反用過去式（were），與過去相反用過去完成式（had + V-pp），表未來願望用 would/could + V。as if / as though（好像）後面也用假設語氣，表示非事實的比喻。 公式：S + wish + S + V-ed (現在) / had V-pp (過去) / would V (未來)
【It's time (that) / would rather (that)】It's time (that) + S + V-ed 表示「該是...的時候了」，暗示現在應該做但還沒做。It's high time 語氣更強。would rather (that) + S + V-ed 表示「寧可...」，用過去式表達與現在事實相反的偏好。 公式：It's time (that) + S + V-ed / S + would rather (that) + S + V-ed
【Should Omission (should 省略)】在表示「建議、要求、命令、堅持」的動詞（suggest、recommend、demand、insist、require、request、propose、order 等）後面的 that 子句中，動詞用原形（即省略 should）。形容詞如 important、essential、necessary、vital 後面的 that 子句也適用此規則。 公式：S + suggest/demand/insist + that + S + (should) + V原形
例句
If I were you, I would study harder.
如果我是你，我會更用功讀書。（但我不是你）
If I were ... I would studyIf she had more time, she could travel around the world.
如果她有更多時間，她就可以環遊世界。（但她沒有）
If she had ... she could travelIf it were not raining, we might go for a walk.
如果現在沒有下雨，我們可能會去散步。（但現在在下雨）
If it were not ... we might goIf I had studied harder, I would have passed the exam.
如果我當時更用功讀書，我就會通過考試了。（但我沒有）
If I had studied ... I would have passedIf she had not missed the bus, she would have arrived on time.
如果她沒有錯過公車，她就會準時到達。（但她錯過了）
If she had not missed ... she would have arrivedIf they had known about the sale, they could have saved a lot of money.
如果他們知道有特賣，他們就可以省很多錢。（但他們不知道）
If they had known ... they could have savedI wish I were taller.
我希望我更高。（但我不是）
wish I wereShe wishes she had accepted the job offer.
她希望她當初接受了那份工作。（但她沒有）
wishes she had acceptedHe talks as if he knew everything.
他說話的樣子好像什麼都知道。（但其實不是）
as if he knewIt's time that you went to bed.
你該去睡覺了。（但你還沒有）
It's time that you wentIt's high time we took action to protect the environment.
我們早該採取行動保護環境了。
It's high time we tookI would rather you didn't tell anyone about this.
我寧可你不要告訴任何人這件事。
would rather you didn'tThe doctor suggested that she take a rest.
醫生建議她休息一下。
suggested that she takeIt is essential that every student be on time.
每位學生準時到是很重要的。
essential that every student beThe manager demanded that the report be submitted by Friday.
經理要求報告在週五前提交。
demanded that the report be submitted常見錯誤
If I was you, I would accept the offer. (✗) → If I were you, I would accept the offer. (✓) 在假設語氣中，不論人稱，be 動詞一律用 were（不用 was）。"If I were you" 是最常見的假設語氣用法。
If I studied harder last year, I would pass the exam. (✗) → If I had studied harder last year, I would have passed the exam. (✓) last year 表示過去的時間，所以是「與過去事實相反」的假設，If 子句要用過去完成式（had studied），主要子句要用 would have + V-pp（would have passed）。
The teacher suggested that he studies more. (✗) → The teacher suggested that he study more. (✓) suggest 後面的 that 子句要用原形動詞（即 should 的省略）。不管主詞是什麼人稱，動詞都用原形 study，不加 -s 或 -es。
快速練習
練習 1
If I _____ a bird, I would fly to you immediately. (A) am (B) was (C) were (D) be
練習 2
If she _____ the warning, the accident could have been prevented. (A) heeded (B) had heeded (C) has heeded (D) would heed
練習 3
I wish I _____ more time to prepare for the exam. (A) have (B) had (C) will have (D) would have
練習 4
The committee recommended that the project _____ immediately. (A) starts (B) started (C) be started (D) is started
練習 5
It's high time you _____ thinking about your future career. (A) start (B) started (C) will start (D) have started
學測應試技巧
學測假設語氣最常考的是：與現在事實相反（If + V-ed, would + V）和與過去事實相反（If + had V-pp, would have V-pp）的區別。
看到 wish、as if、It's time that 等關鍵字就要想到假設語氣。
suggest、recommend、insist、demand 等動詞後面的 that 子句用原形動詞（should 省略），是學測熱門考點。
假設語氣中，be 動詞一律用 were，不論主詞是第幾人稱。這點很容易在選擇題中被測試。
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