高密度聚乙烯管用于道路下排水管道铺设，当槽深小于3m ，管径 300mm ≤ DN ≤1000mm ，沟槽的最小宽度应为() mm 。
A. De + 400
B. De + 600
C. De + 800
De＋ 1000
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Part of the reason why the Internet becomes popular is that ______.
A. more and more people send messages over it
B. new message-searching tools are developed
C. the Internet is not monopolized by anyone
D. there is no authority over the Internet
Which group of people are advised to hold s health insurance？
A. Those who can't afford the medical debts.
B. Those who run private businesses.
C. Those who are above 65 years old.
D. Those who are under 65 years old.
A．He'll give the quiz at a later time.B．The quiz will be very short.C．The quiz won't b
A. He'll give the quiz at a later time.
B. The quiz will be very short.
C. The quiz won't be ready until Thursday.
D. He'll score the quiz quickly.
The Internet was ______.
A. mainly used in the academe circle before it found wide application
B. really a set of "communication protocols" before widely applied
C. restricted to domestic users before it found wide application
D. controlled by a central authority before widely applied
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