Matt is the boy who plays the guitar.

Explanation:

WH-questions are questions starting with WH-words including: what, when, where, who, whom, which, whose, why and how.

What: used to ask about things

- What are you doing?

- What do you think about the movie?

When: used to ask about time

- When will the meeting start?

- When are you leaving?

Where: used to ask about places

- Where’s my bag?

- Where do you live?

Who: used to ask about people

- Who do you love the most in your family?

- Who told you that story?

Whom: used to ask about people (object of verb)

- Whom did you see in the morning? I saw Mr. Mark, my English teacher.

- Whom was Jim talking to? He was talking to Jack, his new roommate.

Which: used to ask about choices

- Which one do you choose? The left or right?

- Of all the drinks in the menu, which one would you like?

Whose: used to ask about possession

- Whose pencil is this? Is it yours?

- Whose books are these?

Why: used to ask about reasons/ causes

- Why did it happen? I didn’t understand.

- Why is he crying?

How: used to ask about manner/ process

- How can you explain this problem? Please tell us.

- How can you get here?