阅读下面短文，简要回答所给问题。

                                              Thumbs Down to Texting 屈指发短信

     Do you have a mobile phone? Do you send text messages to your friends and family?

    Text messaging or "texting" is becoming very popular. But, scientists have discovered that texting can

  give us problems with our hands. Be careful! Too much texting can cause swelling (肿胀) in our

 thumbs.  Our thumbs were not made for pushing small buttons, over and over.  Scientists call this problem

  RSI.  We spoke to a doctor called Harriet Wilson, who treats many sick people with RSI. She says we

 need to see how much time we are spending in typing text messages.  If we are spending more than 10-15

  minutes at once, we could have problems in the future.

     As mobile phones develop, they are getting smaller with buttons closer together. Texting with a smaller

  phone is worse than using a larger phone with bigger buttons.Using a computer keyboard and playing

 video games can cause the same problem.  So more and more people could find themselves with RSL 

 Among them, most are university students and teenagers, as they do not know the risks of spending so

 much time using computer, video games and mobile phones. If we don't do something about this, too

 many young people could grow up in terrible pain.

    Note: RSI abbr .肢体重复性劳损 (repetitive strain injury).

1. What is becoming very popular now according to the passage?

    ______________________________.

2. Does the word "once" mean "one time" in the second passage?

    ______________________________.

3. What kind of people are easier to have the problem of RSI?

    ______________________________.

4. What can also cause RSI besides texting?

    ______________________________.

5. Which is easier to cause the problem of RSI,  using smaller mobile phones or larger ones?

    ______________________________.