词形转换：从句子选词形 · PET / B1
天天向上 · 原创语法学习讲义
先判断句子需要什么词性和意思，再选择常见词形；作为 B1 语言能力训练，不把它冒称某个独立考试题型。
看句法空位
冠词或所有格后常需要名词；be / seem / feel 后常用形容词；修饰动作常用副词。
We need more information before making a decision.
作决定之前我们需要更多信息。
information / decision 是名词，不可仅凭中文直译猜词形。
常见词族
decide→decision；explain→explanation；success→successful→successfully；care→careful→carefully。
The team completed the task successfully.
团队成功完成任务。
-ly 常形成副词，但 friendly 是形容词；fast 也可以直接作副词。
后缀改变意义
-ful 常表示有某性质，-less 常表示缺少；-ed / -ing 形容词注意感受者与引起感受的性质。
The instructions were confusing, so I felt confused.
说明让人困惑，所以我感到困惑。
一个人也可以 be interesting：意思是这个人有趣，不是人就必须用 -ed。
前缀与拼写
unhappy、impossible、incorrect、disagree 等要作为实际词汇核对；变词时同时留意拼写与可数性。
It is impossible to finish without accurate information.
没有准确信息就不可能完成。
本课不把词形转换当成机械拼后缀游戏；先读语境再核对词典。
语境练习
1. We made an important ___ after the meeting.
A. decisively
B. decide
C. decision
2. Please read the instructions ___.
A. care
B. carefully
C. careful
3. The event was very ___.
A. success
B. successful
C. successfully
4. The journey was tiring, so we felt ___.
A. tired
B. tire
C. tiring
5. It is ___ to enter without a valid ticket; the gate will not open.
A. possibility
B. impossible
C. possible
6. Choose the correct sentence.
A. The staff were friend and helpfully.
B. The staff were friendly and helpful.
C. The staff spoke friendlyly and helpful.
7. Thank you for your clear ___.
A. explain
B. explanation
C. explainingly
8. “He is an interesting speaker.” This means:
A. The sentence is wrong because he is a person.
B. His talks are likely to hold people’s attention.
C. He is necessarily feeling bored.
答案与解释
1. C · decision
冠词 an 与形容词 important 后需要名词 decision。
2. B · carefully
修饰 read 的方式，使用副词 carefully。
3. B · successful
was very 后需要形容词 successful。
4. A · tired
felt 后描述感到疲惫，用 tired。
5. B · impossible
后文表无法进入，需要否定形容词 impossible。
6. B · The staff were friendly and helpful.
friendly 和 helpful 都是形容词，可在 were 后描述人员。
7. B · explanation
your clear 后需要名词 explanation。
8. B · His talks are likely to hold people’s attention.
interesting 可描述一个人有趣、能吸引注意，不是只能用于物。
表达任务
写一段对社团活动的评价，使用 success / successful / successfully 中的两个词形、一对 -ed / -ing 形容词，以及一个否定前缀词。
□ 词形由句法位置和意思共同决定。
□ -ed / -ing 描述的含义正确。
□ 前缀、后缀和拼写是实际存在的常用词。
参考表达
Our workshop was a success because everyone had a chance to try something new. The teacher explained the steps clearly, and most groups completed their models successfully. At first, the instructions seemed confusing, so a few students felt confused. However, it was not impossible to continue. We asked for a clearer explanation and helped each other. By the end, everyone felt more confident.
难度范围参照 Cambridge B1 Preliminary for Schools；本站原创练习，并非官方试卷。