道路运输过程中,经常导致事故的危险源主要集中在()上。
A.行车环境不安全因素
B.道路的不安全因素
C.驾驶员的违法行为
D.运输企业安全管理不善
参考答案:C
抗原物质经哪种途径进入机体引发的免疫应答能力最强()
A.肌内
B.皮内
C.腹腔
D.静脉
E.口服
用所给单词的适当形式填空。
1. Peter likes matchbox covers. He has a large ____ (collect).
2. The little boy is ____ (interest) in model planes.
3. The Spring Festival is as ____ (excite) as Christmas.
4. Life is much ____ (difficult) for them than before.
5. Please help ____ (you) to some chicken, boys and girls.