Which is punctuated correctly?

Neither they both don’t start with a capitol.

You should only use one punctuation mark unless you are sending an email or something else informal. The question mark implies that the main aim of the sentence is to gain information:

“What are you doing?”

“I’m just about to go out to the store. What are you up to today?”

The exclamation mark implies that the person speaking is shocked and can see what the person is doing

“What are you doing!”

“Nothing, I just wanted to see what the inside of the cat looked like!”

You get the point!

It’s the second one. You don’t need the exclamation point unless something amazing happened. Like this.

Whoa look at that!

both are ok, it depends on what emotion u want to evoke. the first one is just u asking a question, and the second one shows that ur upset.

it can be either. because…What in the world are you doing! is like really mad or frustrated. and What in the world are you doing? is asking what you are doing not exclaiming it. i doubt ur teacher will count it wrong if you put either one.

What in the world are you doing?

to use the (!) you need to use Caps