语法点：情态动词 must 与 have to (must & have to)
must 和 have to 都表示“必须”，但侧重点不同。must 表示说话人主观上认为有必要，或用于推测（“一定是”）；have to 表示客观情况要求，比如规则、工作安排。must 没有过去式和将来式，要表达“过去必须”“将来必须”时，只能用 had to / will have to。本课的 Jennifer 因为演戏“不得不”穿各种衣服，正是 have to 的典型用法。
结构
| 形式 | must | have to |
|---|---|---|
| 肯定 | She must appear in a red dress. | She has to wear short socks. |
| 否定 | She mustn't tell anyone.（禁止） | She doesn't have to tell anyone.（不必） |
| 疑问 | Must she wear socks? | Does she have to wear socks? |
| 过去 | —（用 had to） | She had to wear short socks. |
| 将来 | —（用 will have to） | She will have to take part in a new play. |
| 推测 | She must be thirty-five.（一定是） | — |
课文中的例句
- [句 2] She must be at least thirty-five years old. — must 表示有把握的推测：“一定有三十五岁了”。
- [句 4] Jennifer will have to take part in a new play soon. — must 没有将来式，将来的“必须”用 will have to。
- [句 6] In the play, she must appear in a bright red dress and long black stockings. — must 表示剧情要求，说话人认为必须如此。
- [句 7] Last year in another play, she had to wear short socks and a bright, orange-coloured dress. — 过去的“不得不”只能用 had to。
- [句 8] 'Darling, it must be terrible to be grown up!' — must + be 再次表示推测：“长大一定很可怕”。
补充例句
- Actresses must learn their parts well. 演员必须把台词记熟。
- Last year I had to appear on the stage every night. 去年我每晚都得登台演出。
- You don't have to wear a bright dress this time. 这次你不必穿鲜艳的裙子。
易错点
- ❌ She musted wear short socks last year. → ✅ She had to wear short socks last year. must 没有过去式，过去用 had to。
- ❌ She will must take part in a new play. → ✅ She will have to take part in a new play. 两个情态动词不能连用，将来用 will have to。
- ❌ You mustn't come if you are busy.（想表达“不必”） → ✅ You don't have to come if you are busy. mustn't 是“禁止”，“不必”要用 don't have to。
- ❌ She must is thirty-five. → ✅ She must be thirty-five. 情态动词后接动词原形 be。