我国从俄罗斯引进的先进防空导弹（），是目前世界上威力最大、最有效的防空系统
A.C-300
B.S-400
C.SS-N-20
D.C-400
参考答案：A
患者，男性，21岁，近2天来出现高热、乏力、腹痛腹泻，头晕1天入院。体检：P90次／分，T39.5℃，面色潮红，眼结膜充血、有出血斑且水肿，皮肤有小的出血点，BP65/45mmHg，WBC18×10/L，Hb140g/L，尿蛋白（+++），患者休克是因为（）
A.败血症
B.血管通透性增加
C.脱水
D.失血过多
E.水肿
Dear Prof. King,
Allow me to introduce to you Mr. Liu, the bearer of this letter. He is one of my former students and is going to enter your institute after graduation here. Will you please give him some necessary guidance about the entrance examination I shall be much obliged if you will show him any favor.
Yours
Alice
What does "obliged" mean（）
