下列哪一种传染病一般呈严格的季节性（）。
A.虫媒传染病
B.寄生虫病
C.呼吸道传染病
D.肠道传染病
E.血液传染病
参考答案：A
人类口腔正常菌群中的主要致龋菌不包括（）
A.变形链球菌
B.黏性放线菌
C.内氏放线菌
D.乳杆菌
E.梭形菌
(66) is defined as the buying and selling of products and services over the Internet. It had included the handling of purchase (67) and funds transfers over computer networks from its inception.
A．Electronicmail
B．Searchengine
C．Multimedia
D．Electroniccommerce
