How long should you wash your hands? Doctors say you should wash for at least (至少) 10 seconds. How can you know the time? This hand washing machine is here to help. It is from China. It’s easy to use. Just put your hand below it. It squeezes (挤出) a soap bubble into your hands. Then, its LED lights flash (闪烁) for 10 seconds. You can rub your hands together and wash up!