Backup and edit/open locally, the file plugins/recaptcha/Lang/English.php
Find the line with of text you want to modify, change it, and maintain the quote marks and semicolons as they were.
Upload the new/changed file to the same location on the server...
Find the line with of text you want to modify, change it, and maintain the quote marks and semicolons as they were.
Upload the new/changed file to the same location on the server...