能穿过胎盘的螺旋体是（）
A.雅司螺旋体
B.回归热螺旋体
C.奋森螺旋体
D.梅毒螺旋体
E.伯氏疏螺旋体
参考答案：D
Many people believe that hunger is only a problem in the developing countries.________， it is a problem all over the world.
A．For one thing
B．In addition
C．As well
D．On the contrary
煤与瓦斯突出按动力现象可分为哪几种类型？
