Who is saying the line

(1) Harry and Hermione dashed across to him.

(2) 'Ron - are you OK? '

(3)'Where's the dog? '

(4) 'Not a dog,' Ron moaned. His teeth were gritted with pain. 'Harry, it's a trap -'

(5)'What-'

(6) 'He's the dog... he's an Animagus ...' Ron was staring over Harry's shoulder. Harry wheeled around. With a snap, the man in the shadows closed the door behind them.

First, who is saying what? I can't determine, Harry or Hermione? And how do you determine, please tell me, it will help.

And why "behind them" not "him"? He was a man.

Solution 1:

(1) Harry and Hermione dashed across to him.

(2) 'Ron - are you OK?' most likely Hermione - females tend to worry about health.

(3)'Where's the dog?' most likely Harry - Harry wants facts.

(4) 'Not a dog,' Ron moaned. His teeth were gritted with pain. 'Harry, it's a trap -'

(5)'What-' - most likely Harry in response to "Harry, it's a trap."

(6) 'He's the dog... he's an Animagus ...' Ron was staring over Harry's shoulder. Harry wheeled around. With a snap, the man in the shadows closed the door behind them. = all three of them.