Answer:
Filling in the subject line is optional, but it is a good practice.
Explanation:
When writing an email, we will find that the subject line is located at the top of the message. We might not know what to do with this line, but it is important that we become familiar with it. This is because, although the subject line is optional, it is still good practice to fill it in. By filling it in, we are able to better communicate what our message is about. This prepares the reader and lets him know what he should expect when opening the message.
