问题 问答题 简答题

简述硫化氢对家畜的危害?

答案

参考答案:

H2S主要是刺激动物呼吸道系统及其他系统粘膜,易溶于动物粘膜仲的水分,与粘液中的钠离子结合生成硫化钠,对粘膜产生刺激作用,引起眼结膜炎,表现流泪,角膜混浊,畏光等症状;H2S还可引起鼻炎,气管炎,咽喉灼伤甚至肺水肿.动物经常吸入低浓度的H2S可出现植物性神经紊乱,偶尔发生多发性神经炎,H2S在肺泡内很快被吸收进入血液内,氧化成硫酸盐或硫代硫酸盐等;游离在血液中的H2S,能进入细胞,和氧化型细胞色素氧化脢中的三价铁结合,使酶失去火星,影响细胞的氧化过长,造成组织缺氧,所以,长期处于低浓度H2S的环境中的家畜体质变弱,抵抗力下降,易发生肠胃病,心脏衰弱等.高浓度的H2S可直接抑制呼吸中枢,引起动物窒息和死亡.

阅读理解

Cast your mind back to the past twenty years and hardly did anyone have their own email account. The Internet had just taken off in 1991 and people were only using office and PC­based email exchanges.

In the mid 1990s external email providers appeared. The most famous of these was Hotmail, the first free email provider and web­based email service. Sabeer Bhatia and Jack Smith launched Hotmail on July 4, 1996. And Microsoft took note of and bought Hotmail for $400 million on December 30, 1997, a nice birthday present for Bhatia who turned 29 that day. It was relaunched as MSN Hotmail and in 2007 was relaunched again as Windows Live Hotmail.

Fast forward the present day and most of us have at least a personal web­based email account. It seems impossible to live without them. One of the biggest advantages of email is the fact that communication has become so much easier, especially with those across different time zones. Email takes seconds to send a message whereas letters, as we used to communicate by, could take weeks. Of course there was the fax, that beeping invention from the 1980s, but it wasn’t as secure as email and you never knew if the person on the other end had picked up your fax or if it had got lost somewhere in the office.

In conclusion, one of the best inventions from the 1990s has to be email. But sometimes people are too closely connected to their email and have a compulsion to check it several times a day. At work, people have become lazy and instead of going to speak to the person sitting next to them, they send an email,causing an in box to pile up with more time spent reading email and responding rather than working. Clearly, an invention that saved time because of its quick and speedy connection can now also cause us to waste a lot of time.

小题1:The earliest web-based email came into being probably _______.

A.in 1991

B.in 1996

C.in 1997

D.in 2007小题2:The author mentions “fax” in the third paragraph in order to tell us that _______.

A.it is exactly as good as email

B.it is much better than email

C.it is less convenient than email

D.it is easier and faster than email小题3:The underlined word “compulsion” in Paragraph 4 probably means “_______”.

A.strong desire

B.common sense

C.special curiosity

D.general idea小题4:Which is the main idea of the last paragraph?

A.We should check email boxes frequently.

B.Lazy people like sending an email.

C.Email brings us great convenience.

D.Good inventions also cause problems.

判断题