A:the fifteenth
B:fifteenth
C:fifteen
艾弗里及其同事研究肺炎双球菌的方法是( )
—— Good evening. I _______ to see Miss Lisa. —— Oh, good evening. I'm sorry, but she is not in.
已知⊙O1,⊙O2的半径分别为5cm、8cm,且它们的圆心距为8cm,则⊙O1和⊙O2的位置关系为( )