题干

同浓度的Na2CO3和NaHCO3溶液pH不相等,使二者pH相等的方法不可行的是(   )

A:向Na2CO3溶液中加适量水

B:向Na2CO3溶液中加适量NaOH固体

C:向NaHCO3溶液中加适量NaOH固体

D:向Na2CO3溶液中通适量CO2气体

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答案(点此获取答案解析)

B

同类题2

根据短文理解,选择正确答案。

    Nowadays airfare isn't getting any cheaper with fuel costs rising every day. Luckily, there are plenty of ways to find the most affordable fares and also avoid paying as many extra charges as possible when you plan ahead.

♦ Getting the best fare

    Fly during the least popular times. Tuesday, Wednesday and Saturday are the slowest days to fly, which means cheaper deals than the rest of the week. You can also find reduced rates on early morning flights, since many people don't like to get up before the sun to get to the airport. Earlier boarding times can also considerably cut down your chances of getting delayed because of other delayed flights or mechanical issues.

    Choose your seat later. Some airlines charge you to pick your seat when you book online, adding even more to the bottom line of your ticket cost. If you show up early on your travel day, you can still have a chance to get suitable seats that others are not willing to pay extra for ahead of time.

    Fly on holidays. You already know that summer is the most expensive time to fly, but the days surrounding holidays can also be crazy. Save big if you're willing to travel on major holidays, such as Thanksgiving and Christmas.

    Don't wait until the last-minute to book. Book too early or too late and you could end up paying more than you need to. The best time to book is between three months and six weeks from when you want to travel.

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♦Avoiding extra fees

    Avoid the upgrade(升级). It's not necessary. Sometimes upgrades are free, but mostly you will be charged for seeking a last-minute bump to first class, and the cost can be very high.

    Fly carry-on only. Baggage fees vary wildly, but almost all airlines charge them and charge big. It's easy to reduce the amount of stuff if you pack less clothes and only travel-sized toiletries. Planning to do a bit of laundry on your trip will also do.

    Pack your own snacks. Unless you're flying internationally, it's rare your flight comes with a free meal. So put some of your own snacks — homemade muffins, fruit and granola bars all make fantastic travel foods — into your bag and eat a lot better, and cheaper, than other passengers.

同类题4

    One afternoon, my son came home from school and asked me, “Are all people the same even if their skin color is different?” I thought for a moment, then I said, “I'll explain. Let's go to a fruit store first. I have something interesting to show you.”
At the store, I told him that we needed to buy apples. And we bought some red apples, green apples and yellow apples.
   After we got home, I told Adam, “It’s time to answer your question.” I put one of each type of apple on the table: first a red apple, followed by a green apple and then a yellow apple. Then I looked at Adam, who was sitting on the other side of the table.
   “Adam, people are just like apples. They come in different colors, shapes and sizes. See, some may not even look as delicious as others.” As I was talking, Adam was examining each one carefully.
   Then, I took each of the apples and peeled them, placing them back on the table, but in a different place.“OK, Adam, tell me which one is the red apple, the green apple and the yellow apple.”He said, “I can’t tell. They all look the same now.”“Take a bite(一口) of each one. See if that helps you tell which one is which.”He took big bites, and then a huge smile came across his face. “People are just like apples! They are all different, but if you take off the outside, they’re pretty much the same on the inside.”“Right,” I agreed. “Just like everyone has their own features but they are nearly the same.”
   He completely got it. I didn’t need to say or do anything else.
   Now, when I eat an apple, it tastes a little sweeter than before. What perfect fruit it is!