高处作业是指距坠落高度基准面（）米以上有可能坠落的高处进行的作业。A、1米 B、2米C

By using (26) , a 600M -byte music CD can be compressed to 50M bytes or less. It can be streamed (downloaded in chunks) so that you can begin listening to the opening bars while the (27) of the file arrives in the background. And, most important, the music files of this kind retain good listening (28) that earlier (29) schemes lacked. That (30) of features makes accessing and distributing music on the web practical for the first time.

A．quantity

B．mass

C．amount

D．quality

你校研究生招录中有人举报某老师违反工作纪律，还向媒体反映了，你是招生负责人，怎么办？

作业人员登高前，检查发现（）质量严重不合格，定为未遂。

A、登高工具

B、安全帽

C、安全带

D、拉线断

需求分析常用的建模方法包括______。
①DFD
②IDEF0
③E-R模型

A) ①②
B) ①②③
C) ②③
D) ①③

含有钾素的化学肥料有哪些？