1. (2017·杭州模拟) 通读下面短文, 掌握其大意,  然后从每题所给的四个选项（A、B、C和D）中, 选出一个最佳选项。  
           Germs (细菌) are1 . You can't 2 them, but they are on your desk, on your computer, and even in the air! Like people, germs move around the world. They fly with us on3. When food, clothes, and other things travel around the world, germs travel, too. Some germs are 4, but some are dangerous. Germs cause illnesses 5 colds and the flu. Warmer Weather Brings Germs     The world's weather is 6. Cooler countries are getting 7, so insects from hot countries can move there. Some of these insects, like mosquitoes, carry dangerous germs. These germs cause headaches, fever, and can8 kill people. Under Your Skin     Your skin protects you 9 germs. It 10 some germs, but not all. They can enter your body when you eat, or when you have a cut. Germs are on your hands, too. They 11 your body when you touch your eyes, nose, or mouth. Fighting Germs     Your immune system protects you, too. When germs get inside your body, your immune system finds and kills them. Special cells move around your body and fight germs. They help you stay 12. 13 cells make antibodies. Antibodies help your body 14  and stop germs.      What can you do to fight germs? You should wash your hands with soap and water. Soap kills many germs, and water washes them15.