i will tell her the good news____i got to the office

问题描述:

i will tell her the good news____i got to the office
A.in the moment
B.the moment
C.the moment as
D.in the moment when
我选择的a,
麻烦解释各个选项

应该是选B
我一到邮局就告诉她这个好消息.能详解下吗the moment 前不需要介词。