A.What is your favorite subject and why?

My favorite subject is music because I like playing the piano.✔

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B.  Hey , How are you?

=> Another way: Your sentence is okay and this is another way of saying it.

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Hey! What's Up? 

It's good.

=> Another way: Your sentence is okay and this is another way of saying it.​

Not much. 

This is skate board.

=> Another way: Your sentence is okay and this is another way of saying it.​

It's a skateboard.​