1. This letter must have been sent by Jack. 2. Some more flowers should be planted by him. 3. Are all the new staff

мysterious man in a black coat.

1. This letter must have been sent by Jack.
— Jack is most likely the person who sent the letter. The use of «must have been» suggests a high degree of certainty.

2. Some more flowers should be planted by him.
— The responsibility of planting more flowers falls on him. The use of «should» indicates a suggestion or recommendation.

3. Are all the new staff trained by her?
— She is responsible for training all the new staff. The use of «by her» indicates that she is the one performing the action.

4. The project will have been finished by us by next Friday.
— We will complete the project by next Friday. The use of «will have been» suggests a future action that will be completed before a specific time.

5. With what was the safe opened by them?
— They used something to open the safe, and we are asking what that something was. The use of «by them» indicates that they were the ones who performed the action.

6. The contestants must be informed about the rules of the game by you.
— It is your responsibility to inform the contestants about the rules of the game. The use of «must be» emphasizes the necessity or obligation of the action, and «by you» indicates that you are the one performing the action.

7. All the beds had been made by her.
— She made all the beds in the past. The use of «had been» suggests a completed action in the past.

8. Has a poem been written for you by Danny?
— Danny may have written a poem specifically for you. The use of «has been» suggests that the action of writing a poem has occurred in the past and the result is relevant in the present.

9. The dog was being fed by the mysterious man in a black coat.
— The mysterious man in a black coat was feeding the dog. The use of «was being» suggests an ongoing action in the past.