下列细菌中最有可能引起人龋齿和牙周炎的细菌是
A．放线菌
B．白喉棒状杆菌
C．乙型溶血性链球菌
D．幽门螺杆菌
E．军团菌
参考答案：A
Though most people know that smoking ________ the risk of cancer,it is still hard for them to give it up.[ ]
A. multiplies
B. adds
C. combines
D. gains
在气温较低或电源电压低于额定电压的地方，日光灯不易启动有何办法？
