问题 单项选择题 A1型题

关于氟的安全性,说法错误的是()

A.6~7岁后才进入高氟区生活,不会出现氟牙症

B.氟牙症多发生在恒牙,乳牙很少见

C.患氟牙症牙数多少取决于牙发育矿化期在高氟区生活的长短

D.氟牙症是由于氟的急性中毒造成的

E.氟牙症属于地方性慢性氟中毒

答案

参考答案:D

解析:6~7岁儿童的恒牙基本发育完全,所以高浓度的氟不会产生氟牙症,所以A正确。氟牙症累计恒牙较乳牙多见,因为乳牙的釉质的发育在出生前,母亲体内的胎盘屏障会防止氟进入胎儿体内,所以B正确。因为氟对牙齿发育的影响是连续性的,所以患氟牙症牙数多少取决于牙发育矿化期在高氟区生活的长短,C正确。氟急性中毒是一次摄入氟量过多所致,与氟牙症无关。氟牙症多由于地方水中含氟量较多所致,所以具有地方性慢性中毒表现,所以E正确。所以此题选D。

单项选择题
阅读理解

Long long ago, there was a man who was good at shooting arrows.He asked the king to declare him as the greatest archer(射手) of the country.The king was about to do so when an old servant of the king said,“Wait,sir.I know an old man who lives in the forest.He is a much greater archer.Let this young man go to him and learn from him for at least three years.”

The man could not believe what the servant said,but he went and found the old man and he was! For three years he learned from him.Then one day,when he thought he had learned everything,the thought arose in him:“If I kill this old man,then I will be the greatest archer.”

The old man had gone to cut wood and he was coming back carrying wood on his shoulder.The young man hid behind a tree,waiting to kill him.He shot an arrow.The old man took a small piece of wood and threw it.It struck the arrow and the arrow turned back and wounded the young man very deeply.The old man came,took out the arrow and said。“I knew that some day or other you were going to do this.That’s why I have not taught you this secret.There is no need to kill me.My Master is still alive,and I’m  nothing before him.You must be  with him for at least thirty years.And he is very old,so go fast! Find the old man!”

小题1:The young archer wanted to kill the old man because_______.

A.he could then become the greatest archer

B.he had nothing more to learn from him

C.the old man refused to teach him everything

D.the king’s old servant ordered him to do SO小题2:What do you think would most probably happen next?

A.The young archer died from the wound soon after.

B.The king declared the young man the greatest archer.

C.The young archer found the old man’s master and killed him.

D.The young archer set off to look for the old man’s master.小题3:What lesson can you learn from the story?

A.Always use a piece of wood to protect yourself from an arrow.

B.You must never try to become better than your teacher.

C.The older a man is,the better archer he usually becomes.

D.There’s always someone better than you in this world.