题干

以下是检查装置气密性的操作,其操作步骤正确的顺序是(   )

①把装置连接好

②两手紧贴容器外壁使容器内的空气受热膨胀

③观察导管口有无气泡冒出

④把导管的一端浸入水中.

A:②④①③

B:③②①④

C:①③②④

D:①④②③

上一题 下一题 0.0难度 选择题 更新时间:2019-05-28 01:09:43

答案(点此获取答案解析)

D

同类题4

阅读下列短文,从每题所给的四个选项(A、B、C和D)中选出最佳选项。

    Is your TV connected to the Internet? What about your chair, or your fridge? Probably they are not. But in the future, most things in your home may be connected, thanks to the so-called "Internet of things".

    The Internet of things may be coming sooner than you think. Earlier this year, Samsung CEO spent a lot of time talking about the Internet things. He said that three years from now, every Samsung product will be part of the Internet of things, no matter whether it's a remote control or a washing machine.

    So, how do household objects that are part of the Internet of things work? Well, think of a common chair. When connected to the Internet, the chair warms up when it knows the user has just walked into the room and is feeling cold.

    An Internet-connected camera could help people feel safer in their homes. It can know people's faces and has an infrared sensor(红外传感器), so even if it's dark it can see when someone passes by and send you a message on your smart-phone to let you know who's there. If the person is someone you don't know, it can tell you that, too.

    But according to MIT Technology Review, whether companies are connecting dog food bowls or safety systems to the Internet, there may be some problems. For example, many early connected-home objects don't have much built-in security, which means they could be hacked(攻击). Moreover, it could be difficult to get these new machines to work together especially when they are made by different companies. To fight this, many companies have joined the Open Interconnect Consortium, which had 45 members by late 2015.

    So, picture this: you enter your home. The temperature changes to make you feel comfortable. Your favorite music starts playing for you. Do you think that this would be a good thing? It may happen sooner than you think.