在双绞线的组网方式中，以太网的中心连接设备是【8】。-我要搜题网

[单选题]设航向信标产生的90Hz调幅信号的调幅度为19%,则CSB信号中90Hz上边带信号和载波信号的振幅比为( )。
A.0.19
B.0.095
C.0.38
D.0.5

[单选题]As adults,it seems that we are constantly pursuing happiness,often with mixed results.Yet children appear to have it down to an art-and for the most part they don't need self-help books or therapy.instead,they look after their wellbeing instinctively,and usually more effectively than we do as grownups.Perhaps it's time to learn a few lessons from them.41_What does a child do when he's sad?He cries.When he's angry?He shouts.Scared?Probably a bit of both.As we grow up,we learn to control our emotions so they are manageable and don't dictate our behaviours,which is in many ways a good thing.But too often we take this process too far and end up suppressing emotions,especially negative ones.that's about as effective as brushing dirt under a carpet and can even make us ill.What we need to do is find a way to acknowledge and express what we feel appropriately,and then-again，like children-move on.42_A couple of Christmases ago,my youngest stepdaughter,who was nine years old at the time,got a Superman T-shirt for Christmas.It cost less than a fiver but she was overjoyed,and couldn't stop talking about it.Too often we believe that a new job,bigger house or better car will be the magic silver bullet that will allow us to finally be content,but the reality is these things have very little lasting impact on our happiness levels.Instead,being grateful for small things every day is a much better way to improve wellbeing.43_Have you ever noticed how much children laugh?If we adults could indulge in a bit of silliness and giggling,we would reduce the stress hormones in our bodies,increase good hormones like endorphins,improve blood flow to our hearts and even have a greater chance of fighting off enfection.All of which,of course,have a positive effect on happiness levels.44_The problem with being a grown up is that there's an awful lot of serious stuff to deal with---work,mortgage payments,figuring out what to cook for dinner.But as adults we also have the luxury of being able to control our own diaries and it's important that we schedule in time to enjoy the things we love.Those things might be social,sporting,creative or completely random（dancing aroud the living room,anyone?）--it doesn't matter,so long as they're enjoyable,and not likely to have negative side effects,such as drinking too much alcohol or going on a wild spending spree if you're on a tight budget.45_Having said all of the above,it's important to add that we shouldn't try too hard to be happy.Scientists tell us this can backfire and actually have a negative impact on our wellbeing.As the Chinese philosopher Chuang Tzu is reported to have said:"Happiness is the absence of striving for happiness."And in that,once more,we need to look to the example of our children,to whom happiness is not a goal but a natural by product of the way they live.43选？
A.Be silly
B.Have fun
C.Express your emotions
D.Don't overthink it
E.Be easily pleased
F.Notice things
G.Ask for help

[填空题]在双绞线的组网方式中，以太网的中心连接设备是 【8】 。

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[填空题]在双绞线的组网方式中，以太网的中心连接设备是【8】。