Here's a short story:

Zhou Yan, a Junior 3 student, wishes he never got a mobile phone. Last week, he went to see a doctor because his arms and fingers were injured. The doctor told him that he had had "mobile phone disease ". A growing number of teenagers are getting "mobile phone disease" because more and more are using mobile phones. Zhou got his mobile phone five months ago. He sent messages to his friends with it all the time, even when going to bed. Zhou started to do badly in exams because he spent too much time playing with his mobile phone. His mom got very angry with him, but he didn't stop playing with the mobile phone until his arms got injured. Yang Ling, a doctor, says that if someone uses his mobile phone too much, like Zhou Yan, he might get "mobile phone disease". If teenagers find their arms or fingers hurt , they should go to see a doctor as soon as possible. Yang says teenagers should try to use their mobile phones less, especially at school. (End of story)

Provide your best guess for the following question. Give ONLY the guess, no other words or explanation.

For example:

Guess: <most likely guess, as short as possible; not a complete sentence, just the guess!>

Here are a few examples of questions and answers:

Question: What should be used less?
Guess: Phones

Question: What type?
Guess: Mobile.

Now answer the following question in the same format.

Question: What hurts?

Arms or fingers.