推測:一定是、不可能、可能

🎯 這一課你會學會

根據線索推測——「他一定很累」「那不可能是真的」「她可能在家」。用情態動詞 must / can't / might 表達你有多確定。這讓你能表達判斷,不只是描述。

💬 先聽一段對話

Amy: Where's Ken? He's not answering his phone.（Ken 在哪?他不接電話。) Coworker: He must be in a meeting. He usually is at this time.（他一定在開會。這時間通常都在。) Amy: Could he be sick?（他會不會是生病了?) Coworker: Maybe, but he can't be far — his bag is still here.（也許,但他不可能走遠——他的包還在這。)

🔑 三個確定程度

• must be(一定是,很確定):He must be tired.（我很肯定他累了)
• can't be(不可能,很確定不是):That can't be true.（不可能是真的)
• might / may / could be(可能,不確定):She might be at home.

🧩 文法點:用情態動詞表達「有多確定」

① 根據證據下判斷,不是講事實,而是「推測」:

• 燈亮著 → Someone must be home.（一定有人在)
• 他都沒回 → He can't be ignoring me on purpose.（不可能是故意的)

② 三個等級:

確定度	用	例句
幾乎確定「是」	must	He must know her.（他一定認識她)
幾乎確定「不是」	can't	He can't know her.（他不可能認識她)
有可能	might / may / could	He might know her.（他可能認識她)

③ ⚠ 否定的確定用 can't,不是 mustn't:

• ✅ It can't be true.（不可能是真的——確定不是)
• ❌ It mustn't be true.（mustn't 是「禁止」,不是「推測不可能」)
• 這是最常錯的:推測「不可能」用 can't,不用 mustn't。

④ 後面接什麼:

• be + 形容詞/地點:must be tired / must be at work。
• 原形動詞:He must know.（一定知道)
• be + -ing(正在):She must be sleeping.（一定在睡)

📒 高頻單字

單字	KK 音標	中譯	例句
must	/mʌst/	一定(推測)	You must be joking.（你一定在開玩笑。)
sure	/ʃʊr/	確定	Are you sure?（你確定嗎?)
probably	/ˈprɑbəbli/	大概	He's probably home.
obvious	/ˈɑbviəs/	明顯的	It's obvious.（很明顯。)
guess	/ɡɛs/	猜	I guess so.（我想是吧。)

🗣️ 發音提醒

• must be 連讀「MUS-bee」(t 幾乎消失);can't be 「KANT-bee」。
• could /kʊd/、might /maɪt/:l 不發音、gh 不發音。
• obvious /ˈɑbviəs/:三音節,重音在前 ob。

✍️ 開口練習

練習 1:must / can't / might?

• The lights are on. Someone ＿ be home.（很確定是)→ must
• He just ate. He ＿ be hungry.（很確定不是)→ can't
• I'm not sure. She ＿ be at work.（可能)→ might

練習 2:抓錯。

• ❌ It mustn't be true. → ✅ It can't be true.

練習 3:看線索推測。

His car is here, so he must ＿. The store is dark, so it can't ＿.

🎒 帶走

• must be(一定是)、can't be(不可能)、might/may/could be(可能)——表達你有多確定。
• 否定的確定用 can't,不用 mustn't(mustn't = 禁止,不是推測)。
• 後接 be + 形容詞/地點、原形、或 be + -ing。

下一課,把推測用到過去:should have / must have / could have——「早該…」「一定是…了」「本來可以…」。