To extract valid email addresses from the given text, we can use regular expressions. The following regex pattern matches standard email address format: ```python pattern = r'[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}' ``` Using this pattern, we can filter out the valid email addresses from the given text: ```python import re text = """ Contact information: 1. John Doe - john.doe@example.com 2. Jane Smith - jane@smith-family.net 3. support@company.co.uk 4. info@subdomain.example.org 5. Invalid email: not.an.email.com 6. Another invalid: @missing-username.com """ pattern = r'[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}' email_addresses = re.findall(pattern, text) # Convert list of email addresses to a comma-separated string emails_csv = ','.join(email_addresses) print(emails_csv) ``` Output: ``` john.doe@example.com,jane@smith-family.net,support@company.co.uk,info@subdomain.example.org ``` This script will extract only valid email addresses from the text and output a comma-separated list without spaces. The regular expression used in this example is not perfect but covers most common cases. There are other more advanced patterns available that are more robust and adhere more strictly to the email address format specification, but they are often quite complex.