下列有关酶的叙述，正确的是 [ ] A．高温和低温均能破坏酶的结构使其失去活性

污水泵的种类很多，在液面以下运行，开泵前不需引水，噪声和振动较小，设备简单占用位置小，所以，应优先选用的是（）。

A.离心污水泵

B.耐酸污水泵

C.耐碱污水泵

D.潜污泵

根据下图回答有关问题：

（1）写出实验①中反应的化学方程式______．

（2）实验②中可观察到铁片的表面______，说明铁的金属活动性比铜______．（填“强”或“弱”）

（3）实验③中可观察到试管中铁钉最先生锈的是______处．（填“a”或“b”或“c”）

（4）你认为防止铁架台生锈的方法有______．（写一点）

以下对政府的说法不正确的是（）

A.政府和国家是基本等同的两个概念

B.政府一般是指由公共当局及其通过政治程序设立的机构组成，并在它的疆域内或管辖地区实施强制的垄断权力

C.政府是按照政治程序设立的一套机构

D.政府具有垄断性和强制性的政治权力及公共权力

锅炉受压元件失效的主要方式有哪些？

Melissa and Love Letter made use of the trust that exists between friends or colleagues.　Imagine receiving an __(71)___from a friend who asks you to open it.　This is what happens with Melissa and several other similar email __(72)___.Upon　running ,such worms usually proceed to send themselves out to email addresses from the victim's address book, previous emails, web pages__(73)___.

As administrators seek to block dangerous email attachments through the recognition of well-known ___(74)____,virus writers use other extensions to circumvent such protection.Executable (.exe) files are renamed to .bat and .cmd plus a whole list of other extensions and will still run and successfully infect target users.

Frequently ,hackers try to penetrate networks by sending an attachment that looks like a flash movie ,which, while displaying some cute animation ,simultaneously runs commands in the background to steal your passwords and give the __(75)__access to your network.

（71）处填（）。

A．attachment

B．packet

C．datagram

D．message