上述患儿最典型的心电图改变是哪一种
A．右心房扩大
B．右心室肥厚
C．左心室肥厚
D．不完全右束支传导阻滞
E．预激综合征
参考答案：B
下列属于微生物的有( )。
A．衣原体
B．螺旋体
C．放线菌
D．立克次氏体
— ____ sweep the classroom yesterday？
—I was playing tennis with my friend．
A．Why not
B．Why didn't
C．Why don't
D．Why didn't you
