单选题 What is vexing the Bush administration and other public-health professionals is the fact that the United States is not particularly well prepared in the event a bird flu pandemic does strike in the near future.

【正确答案】 C
【答案解析】题中vex使烦恼，C项的annoy“使苦恼”与之相符。tickle逗笑，使高兴；encourage鼓励；calm使平静，使镇定。