Present perfect continous

Who are they? What have they been doing? 

Nick has been playing the game of marbles since he was 5 years old. He likes to play marbles. He plays with the other kids. He also teaches other kids how to play the game. 

Lately, he has been teaching Brian how to play marbles. He has been teaching Brian all the rules of the game. He has been teaching Brian how to win.

Brian is Nick's friend. Recently, he has been learning to play marbles. He has been wishing to play the game for many years. The past few days, his friend, Nick, has been teaching him how to play marbles. It is a fun game.

	Rewrite the following sentences as negative sentences, yes/no questions, WH-questions (using the underlined word or phrase) and tag questions.
Examples for the sentence “Walter has been washing the car for 30 minutes.” Negative: Walter has not been washing the car for 30 minutes. Yes/No Question: Has Walter been washing the car for 30 minutes? WH-Question: Who has been washing the car for 30 minutes? Tag Question: Walter has been washing the car for 30 minutes, hasn't he?