題目性質：自編仿真題——題目、材料、選項、數據與情境均為按課程標準與聯招常見考點獨立編寫的原創仿真題，非真題原文，未取自任何題庫、教輔或試卷；解析與採分點為教研整理，非官方評分標準。
一、考點定位與做題順序
遇到四個情態動詞都能填，先別比詞義，比兩件事：一是確定性（must 幾乎斷定 ＞ may/might 可能 ＞ can not 否定性斷定），二是時間指向（對過去的推測用「情態 + have done」，對現在用「情態 + 動詞原形」）。再把第三類分開：should have done 不是推測，是「本該做卻沒做」的遺憾/責備；would rather 是偏好，不表推測。
三步判斷：看語境給了多少證據（有硬線索才配 must）→ 看動作發生在何時（過去用 have done）→ 看句子要的是推測、義務還是偏好。下面短文為自編示意文本，人物、社團、時間與數據均虛構。
二、逐題精講
題1
題1 五空完形（每空四選一）
自編短文：When the archive box came back, its label was soaked and the ribbon gone. Ms. Ren said the box (1) ___ have been left near the open window during the storm — the sill was still wet, and no one else had a key. Yet Li was less certain: the caretaker (2) ___ have moved it to the corridor earlier, so the damp (3) ___ not have come from the window at all. What puzzled us was the register: we (4) ___ have signed it out on Friday, but the line was blank. Ms. Ren smiled: "I (5) ___ rather check the log than guess."
(1) A. must B. may C. should D. would
(2) A. must B. might C. can D. need
(3) A. must B. should C. may D. would
(4) A. must B. should C. might D. could
(5) A. had B. would C. could D. must
解析
(1) A. must。 後文給了兩條硬線索：窗臺仍溼、別人沒有鑰匙 → 說話人幾乎斷定，用 must have been left。B may 語氣太弱，與「no one else had a key」的排他證據不匹配；C should have been left 表「本該被放在（卻沒）」，語義反了；D would 不表對過去的確定推測。(2) B. might。「Li was less certain」明說不確定性下降，且是另一種可能的解釋，用 might have moved。A must 與 less certain 衝突；C can have moved 一般不用於肯定句表過去推測（多用於疑問/否定）；D need have moved 表「本不必」，不搭配。
(3) C. may。 承接上一句的另一解釋，「潮氣可能根本不是從窗子來的」：may not have come 表「可能沒……」。關鍵辨析：must not have done 在標準用法中不作「一定沒……」的推測（否定性斷定要用 can not / could not have done），故 A 不可選；B should not have come 是「本不該來卻來了」的責備；D would not 不表推測。
(4) B. should。「登記冊上那一行是空的」＋「What puzzled us」提示本該做而未做的遺憾 → should have signed it out（我們本該在週五登記借出）。A must have signed 與「line was blank」矛盾；C/D 只表可能性，寫不出「本該」的落差感。
(5) B. would。 固定搭配 would rather do A than do B（寧願 A 而不願 B），後接動詞原形 check / guess，正是原句形式。A had rather 非標準搭配（had better 才是另一結構）；C could rather、D must rather 均不成立。
答案 (1) A must (2) B might (3) C may (4) B should (5) B would
採分點 每空 1 分；另計：(1) 指出兩條硬線索支撐 must 1 分；(2) 由 less certain 定 might 1 分；(3) 說明否定性斷定須用 can/could not have done、must not have done 不表該義 1 分；(4) 區分 should have done 的「本該未做」與推測 1 分；(5) would rather…than 後接原形 1 分。
易錯點 見「不確定」就一律填 may，漏看 (1) 的排他證據；把 must not have done 當成「一定沒」；把 should have done 當推測；把 would rather 與 had better / would like 混用；忽略 have done 與動詞原形分別對應過去與現在。
題2
題2 辨形改錯與語氣改寫
(1) 改正下列三句並說明理由：
a) The sill was dry and the box was damp; the rain must not have reached it.
b) We should have signed the register out on Friday — and in fact the line shows we did.
c) I would rather to check the log than to guess.
(2) 把「Someone left the box near the window.」改寫為兩句：一句表對過去的幾乎斷定，一句表對過去的低確定推測；並說明兩句各自需要什麼樣的上下文證據才站得住。
解析
(1) a) 改為 The rain can not / could not have reached it. 對過去的否定性斷定用 can not / could not have done；must not 是「禁止」（must not do），或在某些變體中表「不準」，不用於「一定沒發生過」的推測。原句證據（窗臺幹、箱子溼）本身指向「雨沒到」，正好需要否定性斷定。b) 改為 We signed the register out on Friday — and in fact the line shows we did.（或刪去後半句、把 should have 換成表已完成的事實陳述）。should have done 預設「實際沒做」，與後半句「in fact…we did」自相矛盾；若確實做了，就不能用 should have。也可改成 We should have signed it out on Friday, but the line was blank. 保留「本該未做」的預設。
c) 改為 I would rather check the log than guess. would rather 後接不帶 to 的不定式（動詞原形），than 後同樣用原形；帶 to 是典型干擾項。
(2) 幾乎斷定：The box must have been left near the window. 需要排他性硬證據：如窗臺仍溼、只有一人有鑰匙、監控或登記顯示無人移過——即「其他解釋都被排除」。
低確定推測：The box may / might have been left near the window. 只需一條相容線索即可（如窗開著、有人習慣把箱子放窗邊），但不能排除其他可能；若上下文出現「別處也可能」，就必須降檔到 may/might，不能硬用 must。
兩句都用「情態 + have + 過去分詞」，因為動作發生在過去；差別全在上下文給出的證據強度，不在動詞形式。
答案 (1) a) must not→can/could not have reached；b) should have 與「in fact we did」矛盾，改為事實陳述或補 but the line was blank；c) 去掉兩個 to，would rather check… than guess。(2) must have been left（需排他硬證據）／may·might have been left（只需相容線索且承認他解）。
採分點 三句改錯各 2 分（改對 1 分＋理由 1 分）；must not 與 can not 的分工 1 分；should have 的「實際未做」預設 1 分；would rather 後原形 1 分；(2) 兩句各 1 分、證據強度說明各 1 分。
易錯點 把 must not have done 當「一定沒」；在 b) 裡只改時態不改預設，仍留矛盾；把 would rather 與 had better / prefer to 混為一談；改寫題兩句都用 must，忽略證據強度差異；忘記對過去推測一律加 have done。
三、規律小結與對照表
| 結構 | 確定性/語氣 | 時間 | 語境要求 |
|---|---|---|---|
| must have done | 幾乎斷定（肯定） | 過去 | 排他硬證據，其他解釋已排除 |
| may / might have done | 可能（低確定） | 過去 | 只需相容線索，須承認他解 |
| can / could not have done | 否定性斷定 | 過去 | 證據指向「不可能發生」 |
| must not do | 禁止（非推測） | 現在/將來 | 不用於「一定沒發生過」 |
| should have done | 本該做卻沒做（遺憾/責備） | 過去 | 預設實際未做，不能與「已做」並用 |
| would rather do than do | 偏好（非推測） | 不限 | 後接動詞原形，不帶 to |
| 情態 + 動詞原形 | 對現在/將來的推測 | 現在/將來 | must be / may be |
這類空三步收口：先數證據，再定時間，最後分清是推測、義務還是偏好。證據排他才配 must，只有一條相容線索就用 may/might；動作在過去一律「情態 + have done」；見到 should have done 先檢查「實際是不是沒做」，見到 would rather 先去掉多餘的 to。特別記住一條：「一定沒發生」是 can/could not have done，不是 must not have done。本文短文、人物與數據均為原創自編示意內容。
四、自測清單
- □ 先數上下文給了幾條證據，排他才用 must；
- □ 對過去的推測一律「情態 + have + 過去分詞」；
- □ 否定性斷定用 can/could not have done，不用 must not；
- □ should have done 預設「實際未做」，與「已做」並用即矛盾；
- □ would rather do A than do B，兩處都用原形、不帶 to；
- □ 四個選項語法都通時，比確定性與時間指向，不比詞義輕重。
