A、It can warn office workers not to frown at work. B、It can reduce the harm of facing computer. C、It can make office ladies’ exp

(20)A growing number of women are developing something called "computer face," a leading cosmetic surgeon said. Dr. Prager said professionals who worked long hours in front of a screen were ending up with hung loose skin, "turkey neck" and deep-set wrinkles on their forehead and around their eyes. The specialist said that, of all his clients, office workers were most likely to show premature signs of ageing. If you are one of the unfortunate people who frown or squint when they are concentrating at the screen, then over time, you will inevitably end up with frown lines. What is perhaps more surprising is the number of women with loose jaws because they are sitting in one position for too long. If you spend most of the time looking down then the neck muscles shorten and go loose, eventually giving you a second neck. We are seeing a lot of women who work in executive jobs in offices who have this problem.(21)Dr. Prager, who has a practice near Harley Street in London, said he encourages his clients to put a mirror next to their computer so they can see if they are frowning at the screen. A generation of younger men and women who had grown up with information technology were developing "computer face" at a much earlier age.(22)Dr. Prager said there were several simple steps which could avoid computer face such as regular screen breaks and stretching the neck muscles.
20. What is called "computer face"?
21. What is the function of the mirror next to the computer?
22. What should office workers do according to Dr. Prager?