阅读理解。 In the US and many other countries. Tipping (给小费) is a way of saying thank-you to someone for his good service. Who do you tip? And how much? Below are some tips (提示) for travelers in the US. 1. Taxi drivers: $2 to $3; you give more if he helps you with your bags. 2. Porters (搬运工): A standard tip (标准的小费) for porters is $1 each bag; more if your suitcases are very heavy. 3. Hotel bellboy (青年侍者): Again, $1 for each bag. Tip him when he shows you to your room. 4. Doorman (看门人): A $1 tip for calling a taxi. However, you may tip more for special service, such as shielding (挡住) you with an umbrella in the rain. You don't have to give the doorman anything just for opening the door or greeting you. 5. Hotel maid (女佣): If you stay for more than one night, $1 each night is standard. 6. Waiters and waitresses: 15-20% of your pre-tax (税前的) bill. In restaurants and bars in the US and Canada, 15% is the standard tip. 7. Tour guides (导游): If a tip is not included in your bill, tip $1 for half-day tour, $2 for a one-day tour, and anywhere from $5 to $10 for a week-long tour. Now, it's sad to say that people have to give tips, even though the service is not good at all. So if you go to the US, remember to carry a lot of change (零钱) for tips. 根据短文内容填空。 1. If a taxi driver helps you with your bag, you should pay for $3 tips. 2. Tip the hotel bellboy dollars if you have 3 bags to carry and you do not need him to show you to your room. 3. If a doorman the door or you, you needn't give the doorman anything. 4. You should give at least dollars to the tour guide if you want a week-long tour. 5. You should give dollars to a tour guide if you need a one-day tour.