how do i replace with some regular expression ?

[ntuan310203]

document.Replace(r"B\.\s+\w+", r"\nB. ....", False, True)
how do i replace with some regular expression
for example i have a piece of answer like this:
A. Content A. B. Content B. C. Content C. D. Content D.
i just want to break line at each position A,B,C,D with a period and space add a certain content after it

[William.Zhang]

Hello,

Thanks for your inquiry.
Please refer to the following tutorial to achieve the need to replace text through regular expressions. If you have any other questions, please feel free to write back.
Find and Replace Text by Regular Expressions in Word in C#, VB.NET

Sincerely,
William
E-iceblue support team