一般对致癌物制定的实际安全剂量在人群中引起的肿瘤超额发生率不超过
A.10-2B.10-3C.10-4D.10-5E.10-6
参考答案:E
阅读短文,用所给动词的适当形式填空,必要时可加助动词或情态动词(10分)
I am John.I am l7 years old,and I live in England.My father works in a horse-riding school.I have been riding since I小题1:________ (be)six.I go horse-riding every Saturday.Now, I can ride quite well.I often小题2:________ (spend)all Saturdays at the riding school.I help to get the horses ready.I also help the new students.
Look,there are some people小题3:_____ (train)horse-riding.The girl named Xinyi小题4:_____ (walk)the horse around(遛马)and getting ready to get onto the horse.She is from China.She looks beautiful.She小题5:_____ (study)here three times.Last time,I helped her move up and down at the same time as the horse.While we were learning how to jump the horse,suddenly she fell off the horse and小题6:_____(hurt)her knees badly.I felt sorry that I小题7:_____(not help)her at that time.I thought she wouldn’t come this Saturday.To my surprise,she came again! What a brave girl! Last month,she小题8:____(invite)to come to England for a fashion show.She said she was glad to have the chance to come here and she enjoyed herself.
Oh,Xinyi is riding towards me.
“Hi,Xinyi! You’re great! I have never seen such a brave girl like you.”
‘Thanks.John! I am leaving for Beijing tomorrow.Thanks for helping me these days.I will never forget the exciting experience.I小题9:________(share)it with my friends.”
“I hope小题10:_____ (meet)you soon.”
以下哪种酸具有强腐蚀性,使用时须做必要防护()
A.硝酸
B.硼酸
C.稀醋酸