Thumbs(大拇指) Down to Texting

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 RSI. 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.

53. What does the word “once” in the second passage mean in English?（回答词数不超过2个）

54. What is becoming very popular now? （回答词数不超过3个）

55. Which kind of mobile phones is easier to cause the problem of RSI? （回答词数不超过4个）