随机选择2岁儿童1000名进行免疫接种预防某病的试验,观察10年,结果表明80%的免

题型:单项选择题

问题:

随机选择2岁儿童1000名进行免疫接种预防某病的试验,观察10年,结果表明80%的免疫接种者未发病,由此研究者认为()。

A.该疫苗预防有效,因为有较高的免疫率

B.不能下结论,因为未设对照组

C.该疫苗预防效果欠佳,因为有20%儿童生病

D.不能下结论,因为未进行统计学检验

E.不能下结论,因为10年观察时间短

考点:疾病控制(医学高级)传染性疾病控制传染性疾病控制题库
题型:单项选择题

发酵现象是由     __    引起的,发酵技术是指利用微生物的      __     作用,运用一些技术手段控制 ___       过程,大规模生产       ______  产品的技术。如:酸奶是  __        发酵的产物。

题型:单项选择题

关于晚期产后出血的描述,正确的是 ()

A.指分娩24小时以后至产后1周内发生的出血

B.剖宫产术后出血常发生在产褥期早期

C.胎盘、胎膜残留引起出血者多见

D.妇科检查子宫大而软,宫口闭合

E.产后滋养细胞肿瘤不会引起晚期产后出血

题型:单项选择题

砂浆锚杆用各种砂浆等级不应()。

A、大于M20

B、小于M20

C、大于M10

D、小于M10

题型:单项选择题

Brian arrived at San Francisco airport two hours before the flight to Paris. He was wearing three shirts, a jacket, two pairs of socks, a pair of shorts, and two pairs of jeans. He was carrying one small backpack, which was very full, but he didn’t have any other luggage. Brian needed to meet a man named Tony before he checked in for his flight. He found Tony near the Air France counter. Tony gave him a round trip ticket and a small package.
"Give this package to Jean Paul at the airport in Paris. He will have a sign with your name on it. I think you can find him easily," Tony said," You don’t have any luggage, right"
"Only this backpack," Brian answered. "You said I could bring one carry on bag. "
"That’s right. One carry on bag is fine. Have a good trip. "
"Thanks. "
is Brian a criminal Not at all. He is an air courier. And he paid only $ 110 for the round trip ticket to Paris. Air couriers get cheap airline tickets because they take important packages and papers to foreign countries. Businesses sometimes need to get packages and papers to people in foreign countries by the next day. Often, the only way they can do this is to use an air courier company. It is not cheap for a business to send a package with an air courier, but it is quick.
Every year about 80,000 people worldwide travel as air couriers. The number of tickets for courier travel is growing by about 10 percent a year. However, air courier travel isn’t for everyone. But if you have very little money, can be flexible about your travel plans, and don’t mind wearing the same clothes for a week, it can be a great way to take a vacation!

The author of the text mainly ______.

A. describes the activities of a law breaker
B. suggests an ideal way to travel
C. argues against the air courier travel
D. tells us about a developing business

题型:单项选择题

脑栓塞()

A.4~12mg 

B.5~12mg 

C.10~20mg 

D.15~40mg 

E.50~120mg

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