搜题请搜索小程序“爱下问搜题”
问题 选择题

小红发现自家的农田出现土壤酸化板结现象，经查阅资料得知：是因为该农 田长期施用化肥硫酸【(NH4)2SO4】的缘故。硫酸铵属于         

A．氮肥

B．磷肥

C．钾肥

D．复合肥

答案

答案：A

题目分析：含有氮元素的肥料称为氮肥，含有磷元素的肥料称为磷肥，含有钾元素的肥料称为钾肥，同时含有氮、磷、钾三种元素中的两种或两种以上的肥料称为复合肥；(NH4)2SO4中含有氮元素，属于氮肥。故选A

点评：本题主要考查化肥的分类方面的知识，解答时要分析化肥中含有哪种或哪几种营养元素，然后再根据化肥的分类方法确定化肥的种类。

单项选择题

The idea of test-tube babies may make you either delighted at the wonders of modern medicine or irritated while considering the moral, or legal, or technological implications of starting life in a laboratory. But if you’’ve ever been pregnant yourself, one thing is certain: You wonder what it’’s like to carry a test-tube baby. Are these pregnancies normal Are the babies normal The earliest answers come from Australia, where a group of medical experts at the Queen Victoria Medical Center in Melbourne have taken a look at the continent’’s first nine successful invitro pregnancies. The Australians report that the pregnancies themselves seemed to have proceeded according to plan, but at birth some unusual trends did show up. Seven of the nine babies turned out to be girls. Six of the nine were delivered by Caesarean section. And one baby, a twin, was born with a serious heart defect and a few days later developed life-threatening problems.What does it all mean Even the doctors don’’t know for sure, because the numbers are so small. The proportion of girls to boys is high, but until there are many more test-tube babies no one will know whether that’’s something that just happened to be like that or something special that happens when egg meets sperm in a test tube instead of a fallopian tube. The same thing is true of the single heart defect. It usually shows up in only 15 out of 60,000 births in that part of Australia, but the fact that it occurred in one out of nine test-tube babies does not necessarily mean that they are at special risk. One thing the doctors can explain is the high number of Caesareans. Most of the mothers were older, had long histories of fertility problems and in some cases had had surgery on the fallopian tubes, all of which made them likely candidates for Caesareans anyway.The Australian researchers report that they are quite encouraged. All the babies are now making normal progress, even the twin with the birth defects.

What concern will the test-tube baby raise according to the passage

A．Whether the pregnancies of test-tube babies would be normal.

B．Whether the test-tube babies would be encouraged.

C．Why the proportion of defected babies is so high.

D．Why the number of Caesareans is so high.
查看答案
单项选择题

聚四氟乙烯生料带适合（）接头的密封。

A、腐蚀性介质

B、管螺纹

C、高温、中压

D、高压
查看答案