Asynchronous Transfer Mode (ATM) is a (16) that promises to change the fabric of local and wide area communications.
The key advantage of ATM is the capability to move voice, data, graphics and (17) at speeds of up to 2 gigabits per second.
An ATM switch allows you to create a (18) network that is completely independent from the (19) configuration of the network.
ATM uses a (20) called cell switching to convert data into fixed length cells of 53 bytes each, so they can be switched very quickly and efficiently.

A．technology

B．video images

C．logical

D．physical

关于直观导入，下列说法不正确的是（）

A.适合于自然科学类内容的教学，人文社会科学类内容的教学则不适合

B.有助于学生在直观感知中生成疑问

C.实物、模型、幻灯、电视等蕴涵的内容必须与新教材有密切的联系

D.观察实物、模型、电视片等过程中，教师要及时提出问题，指明学生观察中的思考方向，促进他们的思维，为学习新教材做好准备