quiz: correct or incorrect

[fourmi]

I don't understand why Q4,8,13,15 and 20, are incorrect in the quiz called correct or incorrect. Could you explain it to me, please?
Thank you

[Tdol]

4- It should be 'at work' (without the article)
8 had better not tell (without 'to')
13 What's the weather like OR how's the weather, but not how...like
15 pay a bill (no preposition)
20 enter the building

[fourmi]

Thank you a lot for your explanations! very clear.

[Tdol]

You're welcome, Fourmi.