题干

短周期元素W、X、Y、Z的原子序数依次递增,a、b、c、d、e、f是由这些元素组成的化合物,d为离子化合物,其结构中还含非极性共价键,m为元素Y的单质,通常为无色无味的气体。上述物质的转化关系如图所示。下列说法正确的是(    )

A:原子半径:W<X<Y<Z

B:阴离子的还原性:Y>W

C:a—定由W、X两种元素组成

D:图中转化过程d物质在作为反应物时均即为氧化剂又是还原剂

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D

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    We all have different ways to navigate (导航) when lost—whether asking a stranger for help, consulting an old-school map or simply following our nose. But on a bike, the risks are higher. One wrong turn or that you're in a traffic jam with two lanes between your bike and the nearest pavement may ruin your good mood. Although cyclists, of course, managed to navigate before smart phones, cyclists can make two choices: a few stay calm and embrace getting lost, and the rest turn to a navigation app.

    Google Maps added a directions function for cyclists in 2015 in the US and Canada, and two years later across Europe. And while there are dozens of other apps now offering a similar service, Google Maps has the demerits for many, so the app seems to be falling behind expectations.

    As someone with no sense of direction, I knew it wouldn't be easy when I started cycling earlier this year. I appreciated that the app gave me two warnings before I needed to turn off a road, and automatically recalculated my route if I accidentally went off course. But still, it wasn't a smooth process. Google Maps thought I could cut across a double carriageway with no breaks in its barrier, assumed I knew what it meant when it told me to “head west”, and thought nothing of taking me the wrong way down a busy one-way street.

    Cyclists don't just want safety—they want convenience. Londoner Robson Smith regularly cycles between Clap ham and the City of London and would like to see Google Maps calculate routes where his bike is allowed on public transport and more choice of the type of routes he can take. “Google tends to calculate the most common and comfortable cycle routes. It would be better to have an option which included the fastest route, regardless of comfort,” he says.

    For this reason, Robson says he uses the app Cycle Streets instead. It offers a choice of four different route modes, based on the type the user wants, and saves previous routes. It also tells you how many calories a route burns, how many traffic lights you wilt encounter, and how busy it is.