The one that shows conversational business writing is:
"Gladys, I'm glad you called. How can I help you today?"
This sentence demonstrates conversational business writing because it uses informal language and a question mark at the end, which indicates that it is a request for information rather than a formal statement. It also uses the first name 'Gladys' instead of the formal 'Ms.' or 'Mr.' followed by the client's last name, which makes the communication seem more personal and less formal.