阅读理解。 You've probably heard that you're not supposed to pour old medications down the toilet or drain(排水沟). That's because drugs can get into the water supply and cause problems for people as well as wildlife. But you can't just throw medicines or unused prescriptions in the trash either. You don't want medications-and your private health information-to fall into the wrong hands. Destroying old medications and then putting them in the trash is the way to go. Here's how: Dump the medicine out of its container into a plastic bag. You don't want to throw away medications in their containers because there is a risk that people looking for drugs, as well as kids or pets, might find them. You can mix different kinds of medicines in the same bag. Just be sure to use a plastic bag that can be tightly sealed. And then seal up the bag and throw it away in the regular trash. Destroy the medications. Add a small amount of water to the bag to dissolve(溶解) the medications. Then, add something that is not food, like dirt. That way, if the medication mix falls into the hands of children, they won't be able to eat it. After you've dealt with the medication following the instructions above, throw the medicine container in the trash. But before you do that, get rid of the label and destroy it. This helps you protect your medical information and keep it private. You don't want your name, address, and other personal information showing up next to the name of the drug you are taking. If you can't remove the label, take a marker and black out(用墨等涂掉) any personal information. A few prescription medications need to be dealt with immediately after they are no longer needed. These should still be washed away down the toilet. If your prescription is one of these, the label on the container should say so. 1．Why can't we pour old medications down the toilet or drain? (No more than 15 words) ________________________________________________________________________ 2．How can the unused medications be destroyed? (No more than 15 words) ________________________________________________________________________ ________________________________________________________________________ 3．Why must you remove the label and destroy it before throwing away the medicine containers? (No more than 11 words) ________________________________________________________________________ 4．What is the main idea of the passage? (No more than 8 words) ________________________________________________________________________