Finding the error: one negative too many
Two negatives make a positive: 不得不 and 不能不 both mean “have to”. Verbs such as 防止, 避免 and 否认 already contain a negative, so a 不 or 没 after them reverses the meaning — a favourite trap in find-the-error questions.
Structure
不得不／不能不 + 动词（＝必须） ｜ 防止／避免 + 不希望发生的事（后面不再加“不”） ｜ 否认 + 事实（后面不再加“没”）
Explanation
Chinese words in this text can be activated to show a dictionary gloss.
Chinese uses double negatives on purpose. means that circumstances leave no choice — ， — and usually sounds reluctant. means that reason or duty requires it: “We cannot leave this alone.” means everyone knows. In each case the two negatives cancel and the meaning is positive, with extra force.
The errors come from negatives that are hidden inside a verb. and mean “keep something from happening”; means “say something is not true”; means “not allow”. Whatever follows them is the thing to be prevented or denied, stated positively. is right. literally means “to prevent the accident from not happening again” — the opposite of what was intended.
The same applies to (right) and (he denies that he did not take it — that is, he admits it), and to against .
A practical check is to count: an explicit or plus a negative verb is two negatives, which comes out positive. If the sentence obviously means something negative, one of the negatives has to go.
Correct
Say each one out loud before moving on. The audio is a reference pronunciation, not a model to imitate exactly — match the tone contour, not the voice.
路上堵车，我们不得不改坐地铁。路上堵車，我們不得不改坐地鐵。
Lùshang (fourth tone, falling) dǔchē, (third tone, dipping) wǒmen (third tone, dipping) bùdébù (fourth tone, falling) gǎi (third tone, dipping) zuò (fourth tone, falling) dìtiě. (fourth tone, falling)···
The roads were jammed, so we had to take the underground instead.
为了防止感冒，出门前最好多穿一件衣服。為了防止感冒，出門前最好多穿一件衣服。
Wèile (fourth tone, falling) fángzhǐ (second tone, rising) gǎnmào, (third tone, dipping) chūmén (first tone, high and level) qián (second tone, rising) zuìhǎo (fourth tone, falling) duō (first tone, high and level) chuān (first tone, high and level) yí (second tone, rising) jiàn (fourth tone, falling) yīfu. (first tone, high and level)···
To avoid catching a cold, it is best to put on an extra layer before going out.
他否认自己拿了那笔钱。他否認自己拿了那筆錢。
Tā (first tone, high and level) fǒurèn (third tone, dipping) zìjǐ (fourth tone, falling) ná (second tone, rising) le (neutral tone) nà (fourth tone, falling) bǐ (third tone, dipping) qián. (second tone, rising)···
He denied having taken that money.
Incorrect — Common mistakes
These sentences are wrong. They are printed here on purpose, each one paired with the repair and the reason, because the error you can recognise is the error you stop making.
Not quite
Incorrect sentence: 为了防止这种事故不再发生，公司制定了新的规定。
Correct
Correct sentence: 为了防止这种事故再次发生，公司制定了新的规定。
Why: 防止 already means “keep from happening”. What follows it is the event itself, stated positively: 防止…再次发生.
Not quite
Incorrect sentence: 他否认自己没拿那笔钱。
Correct
Correct sentence: 他否认自己拿了那笔钱。
Why: 否认 is already negative. With 没 the sentence says he denies *not* taking it — the opposite of what is meant.
Not quite
Incorrect sentence: 我们要避免不出现同样的错误。
Correct
Correct sentence: 我们要避免出现同样的错误。
Why: What is avoided is the mistake itself: 避免出现错误. 避免不出现 would mean avoiding the absence of mistakes.
Compared with
Most errors with this pattern are not errors about this pattern — they are a neighbouring pattern arriving at the wrong moment. Read these side by side.
The beginner point is about which negative to use, 不 or 没. This one is about how many. Choosing between 不 and 没 depends on time and on the verb; counting negatives depends on meaning — on noticing that 防止, 避免, 否认 and 禁止 already say “not”.
Negation: 不 versus 没(有) →Often confused with
Finding the error: saying the same thing twice
大约／大概 + 数量（不再加“左右”） ｜ 超过 + 数量（不再加“以上”） ｜ ……的原因是 + 小句（不再加“因为”“造成的”）
More →Mini quiz
Question 1 / 3Total score: 0
What does this sentence mean?
这个会我们不能不去。