The national putonghua exam is coming again, and I can't pronounce a word.

I suggest you read four tones. Some words have been misinformed in long-term pronunciation and become correct pronunciation. If you read them according to the correct pronunciation, sometimes you will say that you misread them. Our teachers are not all models of pronunciation. For example, the pronunciation of "what" is four tones. Now, let's read it twice. If you read four times, people will laugh at you, and not a few, including your last name. For reference.