旅游宏观经济效益的特征是（）
A.环保性和层次性
B.多样性和地域性
C.协调性和灵活性
D.综合性和复杂性
参考答案：D
—What's wrong with your uncle, Mary?
—He's ill. A doctor _ . [ ]
A. has to look for
B. is being operated on
C. has been sent for
以下（）疫苗中含有氢氧化铝佐剂。
A、基因重组乙肝疫苗
B、风疹疫苗
C、白破二联疫苗
D、乙脑减毒活疫苗
