Answer:
address block.
Step-by-step explanation:
A recipient of a letter can respond to it if they have sufficient information about the sender. This is found in the address block section of the letter. It includes the individual's or organization's name, the individual's title, the city, state, zip code and the country of residence. The receiver is therefore able to respond by writing back to the same address contained in the aforementioned section of the letter hence leading to effective communication.