Answer:
1) I can't grant your request of increasing your allowance for 40%, for some reason. I can only give you a 20% increase, take it or leave it.
2) He once cheated on her, keep an eye on him.
3) She often fell sick, please look after her.
4) It's raining cats and dogs. I didn't expect it would rain this much, the sun is straight this morning.
5) Look at her blue eyes, she really stands out from the crowd.