How to remove every line that starts with a specific text - WRITER

My writer document consists of hundreds of blocks of text as below, written under WRITER. Every line ends with a carriage return. I would like to completely remove every line that starts with “B:” and with “C:” and leave no blank line between the left out lines. {please note that there are no empty lines between the text lines in the examples below - I just wrote them this way to be easier to read in the post}

Is there any way to remove them with Find&Replace? Maybe with a regular expression, but I could not find out which one.

Original text in Writer:

A: nonono [carriage return]

B:nonono [carriage return]

C:nonono [carriage return]

D:nonono [carriage return]

Desired text after Replace:

A:nonono [carriage return]

D:nonono [carriage return]

Thank you very much for any suggestion.

^(B:|C:).*$ → nothing

Please note that this replaces the lines with empty lines. You can later replace regex ^$ with nothing to get rid of empty paragraphs.

Thank you! That did the trick.

Gauchão, maybe you want to mark Mike’s answer and close the question?